A by-election was held for the New South Wales Legislative Assembly seat of Neutral Bay on Saturday 15 December 1945. It was triggered by the death of the Leader of the New South Wales Liberal Party and Leader of the Opposition, Reginald Weaver, who died a week after suffering a mild heart attack in the Legislative Assembly chamber. The seat was subsequently won by barrister Ivan Black (Liberal). Neutral Bay being a safe Liberal seat, the Labor Party chose not to field a candidate.