The 1991 NCAA Division I lacrosse tournament was the 21st annual tournament hosted by the National Collegiate Athletic Association to determine the team champion of men's college lacrosse among its Division I programs, held at the end of the 1991 NCAA Division I men's lacrosse season.

North Carolina defeated Towson State in the championship game, 18–13, completing a perfect season (16-0) while also capturing the program's fourth NCAA national title.

Towson State, coached by Carl Runk, became the first unseeded team to reach the NCAA Division I lacrosse finals.

The Tigers got as close as 12–11 at the start of the 4th quarter, scoring 5 straight goals.

Despite these efforts, North Carolina controlled the remainder of the game, winning the national title for the first time since 1986.