Company: IONQ
Filing Date: 2025-07-07
Form Type: 424B5
Source: 0001193125-25-155889
Chunk: 1

Company: IonQ, Inc.
Filing Date: 2025-07-07
Form: 424B5
Chunk 1
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 page 8 of the accompanying prospectus and “Description of Warrants” on page S-13of this prospectus supplement and page 20 of the accompanying prospectus for a more complete description of the securities offered hereby. Our common stock is listed on the New York Stock Exchange (the “NYSE”) under the symbol “IONQ.” We do not intend to list the Warrants on any exchange. On July 3, 2025, the last reported sale price of our common stock on the NYSE was $44.39 per share.

|                                  |     | Per share(1) |         |     | Per        
 Pre-Funded 
 Warrant    |         |     | Total |                |
|:---------------------------------|:----|:-------------|--------:|:----|:-----------|--------:|:----|:------|---------------:|
| Public offering price            |     | $            | 55.4900 |     | $          | 55.4900 |     | $     | 999,999,994.85 |
| Underwriting discounts(2)        |     | $            |  1.1098 |     | $          |  1.1098 |     | $     |  19,999,999.90 |
| Proceeds, before expenses, to us |     | $            | 54.3802 |     | $          | 54.3802 |     | $     | 979,999,994.95 |

| (1) | The Series A Warrants are being offered for no additional consideration. The above proceeds do not include 
 shares of common stock that may be issued upon the exercise of the Warrants.                               |

| (2) | See “Underwriting” for a description of all underwriting compensation payable in connection with this 
 offering.                                                                                             |

Investing in our common stock involves risks. See “ Risk Factors” beginning on page S-5of this prospectus supplement, page 4 of the accompanying prospectus and “Item 1A—Risk Factors” of our most recent report on Form 10-Kor 10-Qthat is incorporated by reference in this prospectus supplement, before making a decision to invest in our common stock. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus supplement. Any representation to the contrary is a criminal offense. Sole Underwriter J.P