Elections were held in the state of Western Australia on 26 February 2005 to elect all 57 members to the Legislative Assembly and all 34 members to the Legislative Council. The Labor government, led by Premier Geoff Gallop, won a second term in office against the Liberal Party, led by Opposition Leader Colin Barnett.

The premier of Western Australia is the head of government of the state of Western Australia. The role of premier at a state level is similar to the role of the prime minister of Australia at a federal level. The premier leads the executive branch of the Government of Western Australia and is accountable to the Parliament of Western Australia. The premier is appointed by the governor of Western Australia. By convention, the governor appoints as premier whoever has the support of the majority of the Western Australian Legislative Assembly, the lower house of the Parliament of Western Australia. In practice, this means that the premier is the leader of the political party or group of parties with a majority of seats in the Legislative Assembly. Since Western Australia achieved self-governance in 1890, there have been 31 premiers. Roger Cook is the current premier, having been appointed to the position on 8 June 2023.