HRR
- Color vision test
- Haploid-relative-risk
- Harrington railway station
- Healy River Airport
- Heart rate reserve
- Henley Royal Regatta
- Hirzebruch–Riemann–Roch theorem
- Historicorum Romanorum reliquiae
- Holy Roman Empire
- Homologous recombination repair
- Hondo Railway
- Horuru language
- Refresh rate
- Rockwell scale
- The History of Rock and Roll