| Abbreviation | Definition |
|---|---|
| HYST | Hull Youth Support Trust |
| HYT | Healthy Youth Transitions |
| HYT | Heights Youth Theatre |
| HYV | Highland Youth Voice |
| IAY | International Association of Youth |
| IBBY | International Board on Books for Youth |
| IBY | International Benedictine Youth |
| ICY | Inner City Youth |
| ICY | Institute for Colored Youth |
| ICYB | Inner City Youth Baseball |
| IDYU | International Democratic Youth Union |
| IEYA | Inspired Ethiopian Youth Association |
| IFAY | International Federation of Anarchist Youth |
| IFFY | Information for Families Youth |
| IFFY | Ipswich Film Festival For Youth |
| IGY | Israeli Gay Youth |
| IGYS | International Geography Youth Summit |
| IHYF | International Hindu Youth Forum |
| IIYL | International Islamic Youth League |
| IKTBN | Institut Kemahiran Tinggi Belia Negara (Malay: National Advanced Youth Vocational Institute; Sepang, Selangor, Malaysia) |