1st Regiment
- 1 Regiment Army Air Corps
- 1 Regiment RLC
- 1st (1st East Prussian) Grenadiers "Crown Prince"
- 1st (Canterbury) Regiment
- 1st (Emperor Alexander) Guards Grenadiers
- 1st (Royal) Regiment of Foot
- 1st Air Defense Artillery Regiment (Indonesia)
- 1st Air Reconnaissance Regiment
- 1st Aviation Regiment (Australia)
- 1st Aviation Regiment (United States)
- 1st Cavalry Regiment (disambiguation)
- 1st Division (disambiguation)
- 1st Evzone Regiment
- 1st Fighter Regiment
- 1st Foot Guards (German Empire)
- 1st Infantry Regiment (France)
- 1st Infantry Regiment (Greece)
- 1st Infantry Regiment (Thailand)
- 1st Infantry Regiment (United States)
- 1st King's Immemorial Infantry Regiment
- 1st Marine Infantry Regiment
- 1st Marine Regiment (United States)
- 1st Massachusetts Infantry Regiment
- 1st Regiment Greek Light Infantry
- 1st Regiment of Foot Guards
- 1st Regiment, Royal Australian Artillery
- 1st Serres Regiment
- 1st Training Aviation Regiment
- 1st Transport Aviation Regiment
- 1st Yugoslav Fighter Regiment
- 3rd Special Forces Division (Greece)
- Durban Light Infantry
- Jäger Regiment 1 (Bundeswehr)
- SS Fortress Regiment 1