The 1990–91 NBA season was the 45th season of the National Basketball Association. The season ended with the Chicago Bulls winning their first NBA Championship, eliminating the Los Angeles Lakers 4 games to 1 in the NBA Finals.

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This season would prove to be Magic Johnson's last full season as a player, as he announced he was HIV positive and retired early the following season (Johnson would play part of the 1995-96 NBA season with the Lakers before permanently retiring).

• The Trent Tucker Rule was adopted. When Trent Tucker hit a walk-off three-point field goal at the buzzer in the previous season, the clock had started with 0.1 left. It prevents any shot to be taken with up to 0.2 seconds left in the period; the lone exception was a tip-in.
• The Los Angeles Lakers failed to win their division for the first time in ten years.
• The Orlando Magic moved to the Midwest Division of the Western Conference, but like the Miami Heat two seasons ago, experienced long road trips back and forth out west. They would move to the Atlantic Division the next season.
• The 1991 NBA All-Star Game was played at the Charlotte Coliseum in Charlotte, North Carolina, with the East defeating the West 116–114. Charles Barkley of the Philadelphia 76ers won the game's MVP award. In the Three-Point Shootout, Chicago Bulls guard Craig Hodges set a record by making 19 consecutive shots, en route to winning his second straight shootout title, and Boston Celtics guard Dee Brown won the Slam Dunk Contest.
• The Minnesota Timberwolves played their first season at the Target Center. They had played their first season at Hubert H. Humphrey Metrodome while Target Center was being built.
• The NBA on NBC began (replacing The NBA on CBS) when the National Broadcasting Company signed a 4-year, US$600 million deal with the NBA. The relationship lasted 12 years (concluding at the end of the 2001–02 NBA season), until The NBA on ABC returned in 2002–03.
• On December 30, the last game of 1990, Scott Skiles of Orlando recorded 30 assists in a game against the Denver Nuggets to set a new NBA record.^[1]
• The Utah Jazz played their final season at the Salt Palace.
• The flagrant foul was instituted.
• For the first time since 1981, the Los Angeles Lakers were not the Number 1 seed in the Western Conference. However they still reached the NBA Finals by upsetting the heavily favored Portland Trail Blazers in six games. They would go on to lose to the Chicago Bulls in five games, their last NBA Finals appearance until 2000.
• During the season, all NBA teams sport patches featuring the American flag on their warmups as an honor to the American soldiers fighting during the Persian Gulf War. Champion became the league's official outfitter.
• The Golden State Warriors became the only seventh seeded team to beat the second seed twice since the 16-team playoff field was introduced seven years earlier. The Warriors defeated the San Antonio Spurs in four games.
• The NBA becomes the first major professional sports league to play outside North America, as the Phoenix Suns and Utah Jazz open the season against each other in Tokyo, Japan.
• On March 9, 1991, the Houston Rockets' Akeem Olajuwon officially changed the spelling of his first name to Hakeem.

• The Indiana Pacers changed their logo and uniforms, adding navy to their color scheme.
• The Minnesota Timberwolves moved into Target Center.
• The New Jersey Nets changed their logo and uniforms.
• The New York Knicks slightly changed their uniforms replacing their alternate "NY" logo on the left leg of their shorts with their current primary logo.
• The Sacramento Kings changed their uniforms, adding a darker blue color from their primary logo.