Williamstown is an electoral district of the Legislative Assembly in the Australian state of Victoria.

It is a 33 km2 urban electorate in the inner south-western suburbs of Melbourne, encompassing the suburbs of Brooklyn, Newport, Spotswood, Williamstown, Williamstown North, South Kingsville, Seaholme, Altona and Yarraville.

[1] It is a very safe seat for the Labor Party, which has held it for all but two terms since 1889 and without interruption since 1904. Notable former members include John Lemmon,[2] who held the seat for a Victorian record 51 years until his retirement in 1955, and former Premiers Joan Kirner[3] and Steve Bracks.

[4] Steve Bracks held the seat from a by-election in 1994 until his surprise resignation on 30 July 2007.

A by-election was held on 15 September 2007, resulting in the election of Labor's Wade Noonan.