The 1990–91 season was Dinamo Zagreb's 45th season in the Yugoslav First League. It proved to be their last season played in the Yugoslav league system. Following the season's completion and due to the breakup of Yugoslavia, Croatian clubs, including Dinamo, decided to leave the league to form Prva HNL. In European competitions Dinamo were drawn to play Italy's Atalanta in the 1990–91 UEFA Cup. After a goalless draw in Bergamo in the first leg, the return leg at Maksimir ended in a 1–1 draw, with Atalanta going through on away goals rule.