The 1991 NCAA Division I Men's Ice Hockey Tournament was the culmination of the 1990?91 NCAA Division I men's ice hockey season, the 44th such tournament in NCAA history. It was held between March 15 and March 30, 1991, and concluded with Northern Michigan defeating Boston University 8 to 7 in overtime. All First Round and Quarterfinals matchups were held at home team venues with the 'Frozen Four' games being played at the Saint Paul Civic Center in Saint Paul, Minnesota. There were 12 teamsthat qualified for the tournament, divided into two regions, East and West. The tournament featured four rounds of play. The three odd-number ranked teams from one region were placed into a bracket with the three even-number ranked teams of the other region. The teams were then seeded according to their ranking with the top two teams in each bracket receiving byes into the quarterfinals. In the first round the third and sixth seeds and the fourth and fifth seeds played best-of-three series to determine which school advanced to the Quarterfinals. In the Quarterfinals the matches were best-of-three series with the victors advancing to the National Semifinals. Beginning with the Semifinals all games were played at the Saint Paul Civic Center and all series became single game eliminations.