The Provisional Government of Autonomous Siberia (PGAS), was an ephemeral government for Siberia created by the White movement.
After the Bolsheviks' seizure of power in Petrograd, All-Siberian Extraordinary Congress of Delegates from Public Organizations, was convened in Tomsk on December 7, 1917. The SR-dominated assembly refused to recognize Soviet authority or its decrees, and during its last session on December 15 called for the convocation of an “all-socialist” Siberian Regional Duma and appointed a Provisional Siberian Council, answerable to the Duma, that would “act as a government.” The opening of the Duma was set for January 8, 1918.
As it happened, the Duma could not open on the date the congress had set for it for lack of a quorum requiring that a minimum of one-third of the delegates, or ninety-three, be present. Many of the delegates had already been arrested by local Bolshevik authorities; others had not been able to reach Tomsk.
When three weeks later, on the night of January 28–29, some forty delegates finally succeeded in meeting, they expeditiously elected a government known as the Provisional Government of Autonomous Siberia (PGAS), under the chairmanship of a young Socialist-Revolutionary P. Derber.
Of the PGAS's twenty ministers, only six had been present at the founding meeting of January 28–29. Two had been in Bolshevik prison, and the rest were scattered throughout Siberia and north China and were chosen in absentia, without their prior consent. Some of them, including Derber, quickly fled to the Far East; others went into hiding.
After the overthrow of the Bolsheviks in Siberia by Czechoslovak Legions and Russian officers organizations, the decision to form the Provisional Siberian Government (PSG) was made on June 29, 1918, in Omsk, at a meeting featuring several members of the PGAS who were still in Western Siberia, including Petr Vologodskii, who was appointed chairman of the Council of Ministers in the new government.
The PSG participated with the Komuch in the State Conference held in Ufa between 8 - 23 September. Some of the 170 delegates also represented other smaller regions. The Komuch suffered two significant defeats while the conference was in progress, losing Kazan on 10 September and Simbirsk two days later. The conference established the short-lived Provisional All-Russian Government (PA-RG).
It effectively ended with the execution of the White leader Aleksandr Kolchak on February 7, 1920.