The 1st Alberta Legislative Assembly was in session from November 9, 1905, to Monday, March 22, 1909, with the membership of the assembly determined by the results of the 1905 Alberta general election which was held on November 9, 1905. The Legislature officially began on November 9, 1905, and continued until the fourth session was prorogued on February 25, 1909, and dissolved the next day on February 26, 1909, prior to the 1909 Alberta general election.

The 1905 Alberta general election was the first general election held in the Province of Alberta, Canada, shortly after the province entered Canadian Confederation on September 1, 1905. The election was held on November 9, 1905, to elect twenty-five members to the 1st Alberta Legislative Assembly.