A by-election for the seat of Cessnock in the New South Wales Legislative Assembly was held on 21 February 1981. The by-election was triggered by the resignation of Bob Brown () to successfully contest the federal House of Representatives seat of Hunter at the 1980 election.
By-elections for the seats of Maitland, Oxley and Sturt were held on the same day.
<includeonly> Bob Brown () resigned to successfully contest the federal House of Representatives seat of Hunter.</includeonly>