The ministries of Western Australia (also known as Cabinets) are the centre of executive power in the Government of Western Australia. They are composed of Ministers who are responsible for one or more portfolios, answer questions on those portfolios in Parliament, and control the operation and administration of departments, authorities, statutes and votes within those portfolios. In a formal constitutional sense, they possess executive power through being appointed to the Executive Council, which contains all members of the Ministry plus a Clerk (who is a staff member and not a member of Parliament), and is headed by the Governor of Western Australia who represents the Crown.
The members of the Ministry are selected by the Premier of Western Australia and then appointed by the Governor from members of the Western Australian Legislative Assembly and Western Australian Legislative Council associated with the governing party or coalition. However, in Labor ministries generally, and the Nationalist Lefroy Ministry (1917–1919), Cabinet's composition is chosen by caucus (a meeting of all Parliamentary members of the party) rather than by the Premier. The Ministry must command the support of the Legislative Assembly—if it either loses a vote of no confidence on the floor of the Assembly, or loses a general election and hence a majority in the Assembly, it is expected to resign and the Opposition Leader, as prospective Premier, is then expected to form a Ministry.
The Constitution of Western Australia does not require Ministers to be members of Parliament, but provides that non-members can only be Ministers for a maximum of three months. This means that when a Government loses an election, the Ministry remains in office (in "caretaker mode") until a new Ministry is presented to the Governor for appointment. For example, when the state election on 6 September 2008 produced a defeat for the Labor government, the Labor ministers remained in office until 23 September 2008, when Premier Colin Barnett appointed a new Ministry.
Until 1948, it was necessary for Ministers, when appointed, to resign their seat in Parliament and re-contest it at a ministerial by-election—these were generally uneventful, but on two occasions, Ministers were defeated—in 1901 when half the Morgans Ministry were defeated, and in 1917 when John Scaddan was defeated upon his appointment to the Lefroy Ministry.
| Name | Premier | Party | Date appointed | Date replaced | Reason for replacement | |
|---|---|---|---|---|---|---|
| Ministerial | 29 December 1890 | 14 February 1901 | Premier entered federal politics | |||
| Ministerial | 15 February 1901 | 27 May 1901 | Lacked support in Assembly | |||
| Leake ministry (1st) | Opposition | 27 May 1901 | 21 November 1901 | Lost confidence motion in Assembly | ||
| Ministerial | 21 November 1901 | 23 December 1901 | Lost confidence motion in Assembly | |||
| Leake ministry (2nd) | George Leake | Opposition | 23 December 1901 | 1 July 1902 | Premier died in office | |
| Opposition | 1 July 1902 | 10 August 1904 | Lost election | |||
| 10 August 1904 | 25 August 1905 | Lost confidence motion in Assembly | ||||
| Ministerial | 25 August 1905 | 7 May 1906 | Premier resigned | |||
| Ministerial | 7 May 1906 | 16 September 1910 | Premier resigned | |||
| Wilson ministry (1st) | Ministerial | 16 September 1910 | 7 October 1911 | Lost election | ||
| Labor | 7 October 1911 | 27 July 1916 | Lost confidence motion in Assembly | |||
| Wilson ministry (2nd) | 27 July 1916 | 28 June 1917 | Ministry collapsed | |||
| 28 June 1917 | 17 April 1919 | Premier resigned | ||||
| Nationalist | 17 April 1919 | 17 May 1919 | Ministry collapsed | |||
| Mitchell ministry (1st) | Nationalist | 17 May 1919 | 15 April 1924 | Lost election | ||
| Collier ministry (1st) | Labor | 16 April 1924 | 23 April 1930 | Lost election | ||
| Mitchell ministry (2nd) | James Mitchell | Nationalist | 24 April 1930 | 24 April 1933 | Lost election | |
| Collier ministry (2nd) | Philip Collier | Labor | 24 April 1933 | 19 August 1936 | Premier retired | |
| Labor | 20 August 1936 | 31 July 1945 | Premier retired | |||
| Labor | 31 July 1945 | 1 April 1947 | Lost election | |||
| 1 April 1947 | 23 February 1953 | Lost election | ||||
| Labor | 23 February 1953 | 2 April 1959 | Lost election | |||
| Liberal-Country | 2 April 1959 | 11 April 1962 | Deputy Premier retired | |||
| Sir David Brand | Liberal-Country | 12 April 1962 | 3 March 1971 | Lost election | ||
| Labor | 3 March 1971 | 8 April 1974 | Lost election | |||
| Liberal-Country | 8 April 1974 | 5 June 1975 | Deputy Premier resigned | |||
| Sir Charles Court | 5 June 1975 | 25 January 1982 | Premier resigned | |||
| Liberal-National Country | 25 January 1982 | 25 February 1983 | Lost election | |||
| Labor | 25 February 1983 | 25 February 1988 | Premier resigned | |||
| Labor | 25 February 1988 | 18 February 1990 | Premier deposed by caucus | |||
| Labor | 19 February 1990 | 16 February 1993 | Lost election | |||
| Liberal-National | 16 February 1993 | 16 February 2001 | Lost election | |||
| Labor | 16 February 2001 | 3 February 2006 | Premier resigned | |||
| Labor | 3 February 2006 | 23 September 2008 | Lost election | |||
| Liberal | 23 September 2008 | 17 March 2017 | Lost election | |||
| Labor | 17 March 2017 | 19 March 2021 | ||||
| Labor | 19 March 2021 | 8 June 2023 | Premier resigned | |||
| Labor | 8 June 2023 |