2003–04 New Jersey Nets season

The 2003–04 NBA season was the Nets' 28th season in the NBA.

After speculating that he would sign with the defending champion San Antonio Spurs in the off-season, Jason Kidd signed a 6-year, $99 million deal to stay with the Nets.

The team acquired All-Star center and two-time Defensive Player of the Year Alonzo Mourning, who missed all of last season due to his worsening kidney condition. However, after just twelve games, Mourning retired on November 25, 2003 due to complications from his kidney disease.

After a 24–22 start to the season, Byron Scott was fired as head coach and Lawrence Frank took over for the rest of the season. With Frank as interim head coach, the Nets overcame adversity, ending the season with a 47–35 record. Despite this, the Nets still managed to repeat as Division Champions and earn the number 2 spot in the Eastern Conference.

After sweeping the New York Knicks in the opening round, the second round pitted the Nets against the Detroit Pistons in last year's Conference championship rematch. However, Detroit would get revenge this time, and would eventually win the series in seven games, ending the 2003–04 season for the Nets. The Pistons would go on to defeat the Los Angeles Lakers in the 2004 NBA Finals.

Following the season, Kenyon Martin was traded to the Denver Nuggets, and Kerry Kittles was traded to the Los Angeles Clippers. Martin and Kidd both represented the Nets at the 2004 NBA All-Star Game, which was held in Los Angeles. This was the first All-Star appearance for Martin.