Sixth Army may refer to:
Germany
- 6th Army (German Empire), a World War I field Army
- 6th Army (Wehrmacht), a World War II field army
- 6th Panzer Army
Russia
- 6th Army (Russian Empire)
- 6th Army (RSFSR)
- 6th Army (Soviet Union)
Others
- Sixth Army (France)
- Sixth Army (Italy)
- Sixth Army (Austria-Hungary)
- Sixth Army (Ottoman Empire)
- Sixth Army (Japan)
- Sixth United States Army