90th Regiment
- 90 Squadron (disambiguation)
- 90th Armoured Regiment (India)
- 90th Division (disambiguation)
- 90th Illinois Volunteer Infantry Regiment
- 90th Infantry Regiment (United States)
- 90th New York Volunteer Infantry Regiment
- 90th Ohio Infantry
- 90th Pennsylvania Infantry
- 90th Regiment of Foot (Perthshire Volunteers)
- 90th Regiment of Foot (Yorkshire Volunteers)
- British Army
- Indian Army
- Royal Winnipeg Rifles
- United States Army