The list of Western Australia Legislative Council by-elections includes every by-election held in the Australian state of Western Australia for the Legislative Council. Prior to the Acts Amendment (Electoral Reform) Act 1987 which came into force at the 1989 election, it was necessary for a by-election to be held to fill any vacancy; they have since been filled by recounts from the previous poll based on a proportional voting system. An imminent Council election often allowed the vacancy to remain until the inauguration of the new Council, usually on the following 22 May.