The team with the highest winning percentage in a single season in NBA history is Bulls 1995- 1996, with a record of 72 wins 10 losses and a winning percentage of 87.8%.

NBA regular season record 10 ranking:

1: Chicago Bulls 72 wins 10 losses (1995- 1996 season).

2: Los Angeles Lakers 69 wins 13 losses (197 1- 1972 season)

3: Chicago Bulls 69 wins 13 losses (1996- 1997 season)

4: Philadelphia 76ers 68 wins 14 losses (1967- 1968 season)

5: Boston Celtics 68 wins 14 losses (1972- 1973 season) [No championship]

6: Boston Celtics 67 wins 15 losses (1985- 1986 season)

7: Chicago Bulls 67 wins 15 losses (1992- 1993 season).

8: Los Angeles Lakers 67 wins 15 losses (1999-2000 season)

9: Dallas Mavericks 67 wins 15 losses (2006-2007 season) [No championship]

10: milwaukee bucks 66 wins 16 losses (1970- 197 1 season).