- Dacia: Trajan conquered Dacia (modern-day Romania) in two wars, from 101 to 102 and from 105 to 106.
- Arabia Petraea: Trajan conquered Arabia Petraea (modern-day Jordan) in 106.
- Mesopotamia: Trajan conquered Mesopotamia (modern-day Iraq) in 115, but it was later abandoned by his successor Hadrian.