The 1991 AFL reserves season was the 72nd season of the AFL reserve grade competition, the Australian rules football competition operating as the second-tier competition to the Australian Football League (AFL).
The premiership was won by the Brisbane Bears after they defeated in the 1991 AFL reserves grand final, held as a curtain-raiser to the 1991 AFL Grand Final at Waverley Park on 28 September. This was the first time a non-Victorian club had won an AFL premiership in any grade, and the Bears' only premiership before the club merged with at the end of the 1996 season.