138th
- 138 (number)
- 138 BC
- 138th (Edmonton, Alberta) Battalion, CEF
- 138th (Lincoln and Leicester) Brigade
- 138th Aero Squadron
- 138th Attack Squadron
- 138th Brigade (People's Republic of China)
- 138th Delaware General Assembly
- 138th Field Artillery Brigade
- 138th Fighter Wing
- 138th Georgia General Assembly
- 138th Guards Motor Rifle Brigade
- 138th Illinois Volunteer Infantry Regiment
- 138th Indiana Infantry Regiment
- 138th Infantry Regiment (United States)
- 138th New York State Legislature
- 138th Ohio Infantry
- 138th Pennsylvania Infantry
- 138th Rifle Division (Soviet Union)
- 138th Street (IRT Third Avenue Line)
- 138th Street (Manhattan)
- 138th Street Bridge
- 138th Street – Grand Concourse (IRT Jerome Avenue Line)
- 138th meridian east
- 138th meridian west
- AD 138
- Connecticut's 138th assembly district
- Pennsylvania's 138th Representative District
- The Simpsons 138th Episode Spectacular
- Third Avenue – 138th Street (IRT Pelham Line)