The 1921 season of Auckland Rugby League was its 13th. Seventy two teams played across its six main grades.[1]
The first grade competition featured seven teams, City Rovers, Marist Old Boys, Maritime, Devonport, Fire Brigade (formerly Grafton Athletic), Newton Rangers, and Ponsonby United. City Rovers comfortably won the senior championship for the 4th time with a 8 win, 1 draw, 0 loss record ahead of Maritime who were unable to repeat their title win from the previous season. City had previously won the title in 1910, 1911, and 1916. This was to be the first of 3 consecutive titles for them. They also won the Roope Rooster knockout competition for the 3rd time after previous wins in 1916 and 1918.