| Document And Entity Information | Jan. 09, 2025 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Jan. 09, 2025 |
| Entity Registrant Name | CG Oncology, Inc. |
| Entity Central Index Key | 0001991792 |
| Entity Emerging Growth Company | true |
| Entity File Number | 001-41925 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 37-1611499 |
| Entity Address, Address Line One | 400 Spectrum Center Drive |
| Entity Address, Address Line Two | Suite 2040 |
| Entity Address, City or Town | Irvine |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 92618 |
| City Area Code | (949) |
| Local Phone Number | 409-3700 |
| Entity Information, Former Legal or Registered Name | N/A |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Ex Transition Period | false |
| Title of 12(b) Security | Common Stock, par value $0.0001 per share |
| Trading Symbol | CGON |
| Security Exchange Name | NASDAQ |
