The 21st Alberta Legislative Assembly was in session from June 12, 1986, to February 20, 1989, with the membership of the assembly determined by the results of the 1986 Alberta general election held on May 8, 1986. The Legislature officially resumed on June 12, 1986, and continued until the fourth session was prorogued on February 17, 1989, and dissolved on February 20, 1989, prior to the 1989 Alberta general election on March 20, 1989.