A by-election for the seat of Greenough in the Legislative Assembly of Western Australia was held on 1 November 1975. It was triggered by the resignation of Sir David Brand (the sitting Liberal member and a former premier) on 21 August 1975. The Liberal Party retained Greenough at the by-election, with its candidate, Reg Tubby, winning 57.3 percent of the two-candidate-preferred (2CP) vote. However, the party suffered a swing of 33.6 points on first preferences, in part due to the entry of two parties that had not stood in Greenough at the 1974 state election (the National Country Party and the Workers Party). The Workers Party was in fact making its electoral debut, and surprised most observers by polling 13 percent on first preferences (only 62 votes fewer than the Labor Party).