| XSD | X-ray Science Division | |
| YALI | Young African Leaders Initiative | |
| YCC | Youth Conservation Corps (older link archive) | |
| YCR | Yellowstone Center for Resources | |
| YE4C | Youth Engaged 4 Change | |
| YFC | Institute of Youth, Family, and Community (changed to IYFC) | |
| YHDP | Youth Homelessness Demonstration Project | |
| YMSM | Young Men Who Have Sex With Men Project | |
| YRBSS | Youth Risk Behavior Surveillance System | |
| YRC | Young Readers Center | |
| YSS | Year of the Solar System (unable to verify 3/16) | |
| YTS | Youth Tobacco Survey | |
| YVPCs | National Centers of Excellence in Youth Violence Prevention (older link archive) | |
| ZBP | Zip Code Business Patterns | |
| ZCTA | ZIP Code Tabulation Areas (older link archive) | |
| ZIP (Code) | Zone Improvement Plan | |