Supplemental Prospectus (Form 424B3)

SUMMARY

This summary highlights selected information included or incorporated by reference in this prospectus supplement and the accompanying prospectus. This summary does not contain all of the information that you should consider before investing in the notes. You should read this entire prospectus supplement and the accompanying prospectus carefully, including the information incorporated by reference, especially the risks of investing in the notes described under "Risk Factors" in this prospectus supplement in addition to the risks described under the heading "Item 1A. Risk Factors" contained in our Annual Report on Form 10-K for the fiscal year ended December 31, 2024, which is incorporated by reference herein, and our financial statements and the notes to those statements incorporated by reference herein before you decide to invest in the notes. See also "Where You Can Find More Information" in the accompanying prospectus.

Our Company

We are one of the world's largest designers, manufacturers and marketers of electrical, electronic and fiber optic connectors and interconnect systems, antennas, sensors and sensor-based products and coaxial, high-speed and specialty cable. We estimate, based on recent reports of industry analysts, that worldwide sales of interconnect and sensor-related products were approximately $250 billion in 2024.

Certain predecessor businesses of the Company were founded in 1932 and the Company was incorporated under the laws of the State of Delaware in 1986. Our Class A Common Stock began trading on the New York Stock Exchange in 1991.

We align our businesses into three reportable business segments: (i) Harsh Environment Solutions, (ii) Communications Solutions and (iii) Interconnect and Sensor Systems. This alignment and segment structure reinforces our entrepreneurial culture and enables clear accountability of each of our business unit general managers, while enhancing the scalability of our business for the future. We have three segment managers who lead our respective reportable business segments, each reporting directly to our Chief Executive Officer.

A description of each of our reportable business segments is as follows:

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Harsh Environment Solutions - the Harsh Environment Solutions segment designs, manufactures and markets a broad range of ruggedized interconnect products, including connectors and interconnect systems, specialty cable, printed circuits and printed circuit assemblies and other products for use in the industrial, defense, commercial aerospace, automotive, communications networks and information technology and data communications end markets.

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Communications Solutions - the Communications Solutions segment designs, manufactures and markets a broad range of connector and interconnect systems, including high speed, radio frequency, power, fiber optic and other products, coaxial and high-speed cable, as well as antennas, for use in the information technology and data communications, mobile devices, industrial, communications networks, automotive, commercial aerospace and defense end markets.

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Interconnect and Sensor Systems - the Interconnect and Sensor Systems segment designs, manufactures and markets a broad range of sensors, sensor-based systems, connectors and value-add interconnect systems used in the automotive, industrial, information technology and data communications, communications networks, defense and commercial aerospace end markets.

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Our overall strategy is to provide our customers with comprehensive design capabilities, a broad selection of products and a high level of quality and service on a worldwide basis while maintaining continuing programs of productivity improvement and cost control. Our principal executive offices are located at 358 Hall Avenue, Wallingford, Connecticut 06492, and our main telephone number is (203) 265-8900. Our website is located at http://www.amphenol.com. The information on our website, however, is not, and should not be deemed to be, a part of this prospectus supplement or the accompanying prospectus.

Recent Developments

CCS Acquisition

On August 3, 2025, we entered into the Purchase Agreement in connection with the CCS Acquisition for an aggregate purchase price of approximately $10.5 billion in cash, subject to customary post-closing

adjustments. The CCS Acquisition is expected to close before the end of the first quarter of 2026 and is subject to the receipt of customary regulatory approvals and the satisfaction of other customary closing conditions. We have obtained committed financing from J.P. Morgan Chase Bank, N.A., BNP Paribas and Mizuho Bank, Ltd. to fund the transaction. We intend to use the net proceeds from this offering, together with cash on hand, borrowings under the Delayed Draw Term Loan Facilities and/or borrowings under our U.S. commercial paper program, to pay the cash consideration for the CCS Acquisition and the payment of fees and expenses related to the CCS Acquisition. Aggregate borrowings under the Delayed Draw Term Loan Facilities and our U.S. commercial paper program are not expected to exceed the amounts available to be drawn under the Delayed Draw Term Loan Facilities. See "Use of Proceeds."

CommScope, headquartered in Claremont, North Carolina, is a global provider of infrastructure solutions for communication, data center and entertainment networks. Under the Purchase Agreement, we will acquire CommScope's CCS Business, which consists of the Data Center Connectivity Solutions business, the Broadband Communications business and the Building Connectivity Solutions business. The Data Center Connectivity Solutions business primarily sells fiber optic interconnect solutions to customers in the IT datacom market, the Broadband Communications business primarily sells fiber optic and other interconnect solutions to customers in the communications networks market and the Building Connectivity Solutions business primarily sells a broad array of interconnect solutions integrated into existing and next-generation building technology in the industrial market. If and when the CCS Acquisition is consummated, we expect to report the CCS Business within our Communications Solutions segment.

The offering of the notes is not conditioned upon the completion of the CCS Acquisition which, if completed, will occur subsequent to the closing of this offering. However, each series of the notes will be subject to a "special mandatory redemption" in the event that (i) the CCS Acquisition is not consummated on or prior to the later of (x) the Outside Date or (y) the Special Mandatory Redemption End Date, or (ii) we notify the trustee under the indenture in writing that we will not pursue consummation of the CCS Acquisition. We refer to each of such events as a "special mandatory redemption event." If a special mandatory redemption event occurs, we will be required to redeem the outstanding notes of each series at the "special mandatory redemption price" equal to 101% of the principal amount thereof plus accrued and unpaid interest from the date of initial issuance, or the most recent date to which interest has been paid or provided for, whichever is later, to, but not including, the special mandatory redemption date. See "Description of the Notes - Special Mandatory Redemption."

Delayed Draw Term Loans

On August 22, 2025, we entered into (i) a three-year, $2 billion unsecured delayed draw term loan credit agreement among us, certain of our subsidiaries, a syndicate of financial institutions and JPMorgan Chase Bank, N.A., acting as the administrative agent (the "Three-Year Delayed Draw Term Loan Facility"; the commitments thereunder, the "Three Year Delayed Draw Term Commitments" and the loans thereunder, the "Three Year Delayed Draw Term Loans"), which is scheduled to mature on the three year anniversary of the funding date, and (ii) a 364-day, $2 billion unsecured delayed draw term loan credit agreement among us, certain of our subsidiaries, a syndicate of financial institutions and JPMorgan Chase Bank, N.A., acting as the administrative agent (the "364-Day Delayed Draw Term Loan Facility" and, together with the Three-Year Delayed Draw Term Loan Facility, the "Delayed Draw Term Loan Facilities"; the commitments under the 364-Day Delayed Draw Term Loan Facility, the "364-Day Delayed Draw Term Commitments" and the loans thereunder, the "364-Day Delayed Draw Term Loans"; the Three Year Delayed Draw Term Commitments and the 364-Day Delayed Draw Term Commitments, collectively, the "Delayed Draw Term Commitments" and the Three Year Delayed Draw Term Loans and 364-Day Delayed Draw Term Loans, the "Delayed Draw Term Loans"), which is scheduled to mature on the date that is 364 days after the funding date. The Delayed Draw Term Loans are undrawn to date and may each only be drawn in a single drawing over the life of the facilities. The Delayed Draw Term Commitments may be permanently reduced, and the Delayed Draw Term Loans may be repaid, in each case, at any time without premium or penalty and, once Delayed Draw Term Loans are prepaid, cannot be reborrowed. We are required to prepay the Delayed Draw Term Loans with proceeds of certain debt incurrences. Interest rates in respect of the Delayed Draw Term Loans are based on a spread over either the base rate or the adjusted term SOFR, which spread varies based on our debt rating. The proceeds from the Delayed Draw Term Loans will be used to finance a portion of the consideration for the CCS Acquisition and certain related costs, fees and expenses. See "Use of Proceeds."

THE OFFERING

The following summary contains basic information about the notes and is not intended to be complete.

For a more complete understanding of the notes, please refer to the sections entitled "Description of the Notes" in this prospectus supplement and "Description of Senior Debt Securities" in the accompanying prospectus. For purposes of the description of notes included in this prospectus supplement and the accompanying prospectus, references to "we," "us" and "our" refer only to Amphenol Corporation and do not include its subsidiaries.

Issuer

Amphenol Corporation.

Securities Offered

$      aggregate principal amount of floating rate Senior Notes due 20  .

$      aggregate principal amount of    % Senior Notes due 20  .

$      aggregate principal amount of    % Senior Notes due 20  .

$      aggregate principal amount of    % Senior Notes due 20  .

$      aggregate principal amount of    % Senior Notes due 20  .

$      aggregate principal amount of    % Senior Notes due 20  .

$      aggregate principal amount of    % Senior Notes due 20  .

The floating rate notes, the 20   notes, the 20   notes, the 20   notes, the 20   notes, the 20   notes and the 20   notes are sometimes referred collectively as the "notes" in this prospectus supplement.

Maturity Date

The floating rate notes will mature on           , 20  , the 20  notes will mature on           , 20  , the 20  notes will mature on           , 20  , the 20  notes will mature on            , 20  , the 20  notes will mature on           , 20  , the 20  notes will mature on           , 20  and the 20  notes will mature on           , 20  .

Interest and Payment Dates

Interest on the floating rate notes will accrue at a floating rate per annum, reset quarterly on each Floating Rate Interest Payment Date (as defined herein), equal to Compounded SOFR, plus    % (as described in "Description of the Notes -  General - Floating Rate Notes"). The 20  notes will bear interest at an annual rate of     %, the 20  notes will bear interest at an annual rate of    %, the 20  notes will bear interest at an annual rate of    %, the 20  notes will bear interest at an annual rate of    %, the 20  notes will bear interest at an annual rate of    % and the 20  notes will bear interest at an annual rate of    %.

Interest on the floating rate notes will be payable quarterly in arrears on      ,       ,        and        of each year, commencing on            , 2026. Interest on the 20  notes is payable semi-annually on       and        of each year,

beginning on            , 2026, interest on the 20  notes is payable semi-annually on     and     of each year, beginning on           , 2026, interest on the 20  notes is payable semi-annually on     and     of each year, beginning on           , 2026, interest on the 20  notes is payable semi-annually on         and        of each year, beginning on            , 2026, interest on the 20  notes is payable semi-annually on       and       of each year, beginning on           , 2026 and interest on the 20  notes is payable semi-annually on       and       of each year, beginning on           , 2026.

Optional Redemption

We may not redeem the floating rate notes prior to maturity at our option. We may redeem some or all of the 20  notes, the 20  notes, the 20  notes, the 20  notes, the 20  notes and the 20  notes from time to time at the applicable redemption prices described in "Description of the Notes - Optional Redemption" in this prospectus supplement.

Special Mandatory Redemption

Each series of notes will be subject to a "special mandatory redemption" in the event that (i) the CCS Acquisition is not consummated on or prior to the later of (x) the Outside Date or (y) the Special Mandatory Redemption End Date or (ii) we notify the trustee under the indenture in writing that we will not pursue consummation of the CCS Acquisition. We refer to each of such events as a "special mandatory redemption event." If a special mandatory redemption event occurs, we will be required to redeem the outstanding notes of each series at the "special mandatory redemption price" equal to 101% of the principal amount thereof plus accrued and unpaid interest from the date of initial issuance, or the most recent date to which interest has been paid or provided for, whichever is later, to, but not including, the special mandatory redemption date. See "Description of the Notes - Special Mandatory Redemption."

Repurchase upon a Change of
Control

The occurrence of a "Change of Control Repurchase Event" (as defined under "Description of the Notes - Change of Control" in this prospectus supplement) will require us to offer to repurchase from you all or a portion of your notes at a purchase price in cash equal to 101% of the principal amount of the notes, plus accrued and unpaid interest, if any, to, but not including, the date of repurchase (subject to the right of holders of record on the relevant interest record date to receive interest due on the relevant interest payment date). See "Description of the Notes - Change of Control" in this prospectus supplement.

Ranking

The notes will:

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be our general unsecured senior obligations;

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be effectively subordinated in right of payment to any future secured indebtedness to the extent of the value of the assets securing such debt;

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be structurally subordinated to any indebtedness of our subsidiaries, including certain of our subsidiaries'

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obligations as borrowers or guarantors under our revolving credit facility and the Delayed Draw Term Loans;

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rank equally in right of payment with all of our existing and future unsecured and unsubordinated indebtedness, including indebtedness under our revolving credit facility, the Delayed Draw Term Loans, our commercial paper programs, the 4.750% Senior Notes due 2026 (the "4.750% 2026 Notes"), the 5.050% Senior Notes due 2027 (the "5.050% 2027 Notes"), the 4.375% Senior Notes due 2028 (the "4.375% 2028 Notes"), the 5.050% Senior Notes due 2029 (the "5.050% 2029 Notes"), the 4.350% Senior Notes due 2029 (the "4.350% 2029 Notes"), the 2.800% Senior Notes due 2030 (the "2.800% 2030 Notes"), the 2.200% Senior Notes due 2031 (the "2.200% 2031 Notes"), the 3.125% Euro Senior Notes due 2032 (the "3.125% 2032 Euro Notes"), the 5.250% Senior Notes due 2034 (the "5.250% 2034 Notes"), the 5.000% Senior Notes due 2035 (the "5.000% 2035 Notes") and the 5.375% Senior Notes due 2054 (the "5.375% 2054 Notes") and with our guarantee of the 0.750% Euro Senior Notes due 2026 (the "2026 Euro Notes") and the 2.000% Euro Senior Notes due 2028 (the "2028 Euro Notes" and, together with the 4.750% 2026 Notes, the 5.050% 2027 Notes, the 4.375% 2028 Notes, the 5.050% 2029 Notes, the 4.350% 2029 Notes, the 2.800% 2030 Notes, the 2.200% 2031 Notes, the 3.125% 2032 Euro Notes, the 5.250% 2034 Notes, the 5.000% 2035 Notes, 5.375% 2054 Notes and the 2026 Euro Notes, the "existing notes") issued by our subsidiary, Amphenol Technologies Holding GmbH; and

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be senior in right of payment to any future senior subordinated or subordinated debt.

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As of September 30, 2025, on a pro forma as adjusted basis after giving effect to this offering, borrowings under the Delayed Draw Term Loan Facilities (assuming borrowing of the full amount available to be drawn under each Delayed Draw Term Loan Facility and no borrowings under our U.S. commercial paper program) and the application of the net proceeds from this offering and the Delayed Draw Term Loans as more fully described in "Use of Proceeds" in this prospectus supplement:

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we would have had approximately $      billion of unsecured and unsubordinated indebtedness (including the Delayed Draw Term Loans, the notes and the existing notes), all of which would constitute senior indebtedness;

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we would have had no secured indebtedness to which the notes would have been effectively subordinated; and

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our subsidiaries (other than Amphenol Technologies Holding GmbH, the issuer of the 2026 Euro Notes and the 2028 Euro Notes, which are guaranteed by us) would have had approximately $31.3 million of indebtedness

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to which the notes would have been structurally subordinated.

Covenants

We will issue the notes under an indenture with U.S. Bank Trust Company, National Association, as trustee. The indenture, among other things, limits our ability to:

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incur liens on Principal Property (as defined under "Description of Senior Debt Securities - Definitions" in the accompanying prospectus);

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engage in certain sale/leaseback transactions; and

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consolidate or merge with or into, or sell substantially all of our assets to, another person.

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These covenants are subject to a number of important exceptions and qualifications. For more details, see "Description of Senior Debt Securities - Covenants" in the accompanying prospectus.

Absence of Public Market for the Notes

Each series of the notes are a new issue of securities with no established trading market. We do not intend to apply for a listing of the notes on any securities exchange or any automated dealer quotation system. Accordingly, we cannot assure you as to the development or liquidity of any market for the notes. The underwriters have advised us that they currently intend to make a market in the notes. However, they are not obligated to do so and any market making with respect to the notes may be discontinued without notice. See "Risk Factors - Your ability to transfer the notes may be limited since there is no public market for the notes, and we do not know if an active trading market will ever develop, or if a market does develop, whether it will be sustained" in this prospectus supplement.

Use of Proceeds

We anticipate that the net proceeds from the offering, after deducting the underwriting discount and offering expenses payable by us, will be approximately $      million. We intend to use the net proceeds from the offering of the notes, together with cash on hand, borrowings under the Delayed Draw Term Loan Facilities and/or borrowings under our U.S. commercial paper program, to pay the cash consideration for the CCS Acquisition and the payment of fees and expenses related to the CCS Acquisition. Aggregate borrowings under the Delayed Draw Term Loan Facilities and our U.S. commercial paper program are not expected to exceed the amounts available to be drawn under the Delayed Draw Term Loan Facilities. The closing of this offering is expected to occur prior to the consummation of the CCS Acquisition. If a special mandatory redemption event occurs, we will be required to redeem the outstanding notes of each series in a special mandatory redemption. Pending payment of the purchase price of the CCS Acquisition, the net proceeds from this offering are expected to be held as cash and cash equivalents. For more information, see "- Recent Developments - CCS Acquisition," "Use of Proceeds" and "Description of the Notes - Special Mandatory Redemption".

Denominations

The notes of each series will be issued in minimum denominations of $2,000 and integral multiples of $1,000 in excess thereof.

Form of Notes

The notes of each series will be issued as fully registered notes, represented by one or more global notes registered in the name of Cede & Co., the nominee of the depositary, The Depository Trust Company ("DTC"). Beneficial interests in the notes will be shown on, and transfers will be effected through, records maintained by DTC and its participants. See "Global Securities" in the accompanying prospectus.

Governing Law

The notes will be governed by the laws of the State of New York.

Trustee, Paying Agent and Calculation Agent

U.S. Bank Trust Company, National Association.

Risk Factors

Investing in the notes involves risks. In considering whether to purchase the notes, you should carefully consider all of the information set forth in this prospectus supplement, the accompanying prospectus, any free writing prospectus with respect to this offering filed by us with the SEC and the documents incorporated by reference herein and therein. In particular, you should evaluate the specific risks set forth in the section entitled "Risk Factors" in this prospectus supplement in addition to the risks described under the heading "Item 1A. Risk Factors" contained in our Annual Report on Form 10-K for the fiscal year ended December 31, 2024, which is incorporated by reference herein. See "Risk Factors" beginning on page S-12 of this prospectus supplement.

SUMMARY HISTORICAL CONSOLIDATED FINANCIAL DATA

The following tables set forth certain of our condensed consolidated financial data. The summary financial information presented below as of and for each of the three years ended December 31, 2024, 2023 and 2022, has been derived from, and should be read in conjunction with, the audited consolidated financial statements and the accompanying notes incorporated by reference in this prospectus supplement. The summary financial information presented below as of September 30, 2025 and for each of the nine month periods ended September 30, 2025 and September 30, 2024 has been derived from our unaudited interim condensed consolidated financial statements incorporated by reference into this prospectus supplement, which include, in the opinion of our management, all normal and recurring adjustments that are necessary for the fair presentation of the results for such interim periods and dates.

The summary historical consolidated financial information may not be indicative of our future performance. You should read the information in conjunction with the section entitled "Risk Factors" contained in or incorporated by reference into this prospectus supplement and accompanying prospectus and in "Management's Discussion and Analysis of Financial Condition and Results of Operations" and our consolidated financial statements and related notes, in each case incorporated by reference in this prospectus supplement and the accompanying prospectus.

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(a)

See "Supplemental Financial Information   Reconciliations of GAAP to Non GAAP Financial Measures" below.

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(b)

Working capital is calculated as total current assets less total current liabilities.

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(c)

Total debt includes long term debt and capital lease obligations and the current portion of long term debt and capital lease obligations.

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SUPPLEMENTAL FINANCIAL INFORMATION
RECONCILIATIONS OF GAAP TO NON-GAAP FINANCIAL MEASURES

Management utilizes the non-GAAP financial measures defined below as part of its internal reviews for purposes of monitoring, evaluating and forecasting the Company's financial performance, communicating operating results to our Board of Directors and assessing related employee compensation measures.

Management believes that such non-GAAP financial measures may be helpful to investors in assessing our overall financial performance, trends and period-over-period comparative results. The following non-GAAP financial measures exclude income and expenses that are not directly related to our operating performance during the periods presented. Items excluded in the presentation of these non-GAAP financial measures in any period may consist of, without limitation, acquisition-related expenses, refinancing-related costs, and certain discrete tax items including but not limited to (i) the excess tax benefits related to stock-based compensation and (ii) the impact of significant changes in tax law. Reconciliations of non-GAAP financial measures to the most directly comparable GAAP financial measures are included below. All non-GAAP financial measures and their most directly comparable U.S. GAAP financial measures presented in this section are on a continuing operations basis only and exclude any results associated with discontinued operations. The following non-GAAP financial information is included for supplemental purposes only and should not be considered in isolation, as a substitute for or superior to the related GAAP financial measures. In addition, these non-GAAP financial measures are not necessarily the same or comparable to similar measures presented by other companies, as such measures may be calculated differently or may exclude different items. Such non-GAAP financial measures should be read in conjunction with our financial statements presented in accordance with GAAP.

The following are reconciliations of non-GAAP financial measures to the most directly comparable GAAP financial measures for the periods presented:

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Note:

All data in the table above are on a continuing operations basis only and exclude results associated with discontinued operations.

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(1)

The definitions of the non-GAAP financial measures used are as follows:

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Adjusted Operating Income is defined as Operating Income, as reported in the Consolidated Statements of Income contained in the financial statements of our Annual Report on Form 10-K for the fiscal year ended December 31, 2024 and the Condensed Consolidated Statements of Income contained in the unaudited financial statements of our Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2025, which are incorporated by reference herein, excluding income and expenses that are not directly related to the Company's operating performance during the periods presented.

Adjusted Net Income from continuing operations attributable to APH is defined as Net Income from continuing operations attributable to Amphenol Corporation, as reported in the Consolidated