The Fourth Hughes Ministry was the fifteenth Australian Commonwealth ministry, and ran from 5 May 1917 to 3 February 1920.

Nationalist Party of Australia

• Rt Hon Billy Hughes, KC MP: Prime Minister, Attorney-General
• Rt Hon Joseph Cook, MP: Minister for the Navy
• Rt Hon Sir John Forrest, GCMG MP: Treasurer (to 27 March 1918)
• Senator Hon George Pearce: Minister for Defence
• Hon William Watt, MP: Minister for Works and Railways (to 27 March 1918), Treasurer (from 27 March 1918), Minister for Trade and Customs (13 December 1918 to 17 January 1919), Acting Prime Minister in Mr. Hughes' absence (April 1918-August 1919)
• Hon Paddy Glynn, KC MP: Minister for Home and Territories
• Hon Jens Jensen, MP: Minister for Trade and Customs (to 13 December 1918)
• Hon William Webster, MP: Postmaster-General
• Senator Hon Edward Millen: Vice-President of the Executive Council (to 16 November 1917), Minister for Repatriation (from 28 September 1917)
• Hon Littleton Groom, MP: Honorary Minister (to 16 November 1917), Vice-President of the Executive Council (16 November 1917 to 27 March 1918), Minister for Works and Railways (from 27 March 1918)
• Senator Hon Edward Russell: Honorary Minister (to 17 January 1919), Vice-President of the Executive Council (from 27 March 1918)
• Hon Walter Massy-Greene, MP: Honorary Minister (27 March 1918 to 17 January 1919), Minister for Trade and Customs (from 17 January 1919)
• Hon Alexander Poynton, MP: Honorary Minister (from 27 March 1918)
• Hon George Wise, MP: Honorary Minister (from 27 March 1918)
• Hon Richard Orchard, MP: Honorary Minister (27 March 1918 to 31 January 1919)