Grigory Mikhaylovich Semyonov, or Semenov, was a Japanese-supported leader of the White movement in Transbaikal and beyond from December 1917 to November 1920, a lieutenant general, and the ataman of Baikal Cossacks (1919). Semyonov was also a prominent figure in the White Terror. U.S. Army intelligence estimated that he was responsible for executing 30,000 people in one year.

The White movement in Transbaikal was a period of the confrontation between the Soviets and the Whites over dominance in Transbaikal from December 1917 to November 1920.