Bill Russell and the 1956 San Francisco Dons were the first NCAA Division I men’s college basketball team to finish the year undefeated with an NCAA tournament national championship.

Over the course of the next 20 seasons, six other teams would go on to end the year unblemished. But not one squad has completed the elusive perfect season since Bobby Knight and the Indiana Hoosiers did so in 1976. The 3-point line didn’t even make its way into the NCAA tournament until 1987.

RELATED: NCAA tournament championship history

UCLA is the only team with multiple perfect national championship seasons with four.

Five teams have finished the regular season undefeated since 1976 — with the most recent being Wichita State in 2014 and Kentucky in 2015 — but each of those squads either lost in their conference tournament or the NCAA tournament. Two of those teams — 1991 UNLV and 2015 Kentucky lost in the Final Four. The 1979 Indiana State team led by Larry Bird made it to the national championship before its first loss.

Undefeated national champions since 1939:
1975-76 Indiana 32-0
1972-73 UCLA 30-0
1971-72 UCLA 30-0
1966-67 UCLA 30-0
1963-64 UCLA 30-0
1956-57 North Carolina 32-0
1955-56 San Francisco 29-0

Here’s a rundown of every undefeated national championship team since 1939, in order from last to first, and a couple stats from each perfect season.

1976 Indiana Hoosiers

Record: 32-0
National Championship: 3rd

The Indiana Hoosiers were led by Associated Press player of the year Scott May, who averaged 23.5 points and 7.7 rebounds per game. Kent Benson (17.3 ppg, 8.8 rpg) was another bonafide star for the Hoosiers. Opening up as the AP No. 1 team, Indiana’s season began with a 20-point thumping of the defending national champion UCLA Bruins, ranked No. 2 at the time. Indiana is one of seven champions to go wire to wire as the No. 1 team.

Indiana would defeat UCLA a second time in the Final Four, then beat Michigan — a team that took the Hoosiers to overtime at Assembly Hall in the regular season — in the national championship game, 86-68. The Hoosiers shot 51.7 percent for the season.