2018–19 Oklahoma City Thunder season

The 2018–19 Oklahoma City Thunder season was the 11th season of the franchise in Oklahoma City and the 53rd in the National Basketball Association (NBA). Nick Collison (who had been with the franchise since it was based in Seattle), retired in May 2018 and was not on the roster for the first time since the 2002–03 season. The only remaining former SuperSonics' active players are Jeff Green and Kevin Durant, both of whom played their rookie seasons with the team in Seattle. Collison's retirement also left Russell Westbrook as the longest tenured Thunder player and last remaining player on the roster from the 2011–12 season in which they won the Western Conference and went to the NBA Finals. On March 20, 2019, the Thunder retired Collison's No. 4 jersey, becoming the first Thunder player and the last former Sonic player to have their jersey retired. The Thunder had the fourth best team defensive rating in the NBA.

Despite speculation that Paul George would sign with his hometown team, the Los Angeles Lakers, in the off-season, George instead re-signed with the Thunder on June 30, 2018, exactly a year after he was traded to the team from the Indiana Pacers. The Thunder then clinched another playoff season due to the Kings loss to the Rockets on March 30.

In the playoffs, the Thunder were eliminated by the Portland Trail Blazers in the First Round thanks to a Damian Lillard series-clinching three pointer over Paul George in Game 5. This marked the third consecutive season the Thunder was eliminated in the First Round, and they are 0–9 in road playoff games since Durant's departure from the team. After 11 years, this season also marked the end of an era as Russell Westbrook was traded to the Houston Rockets following this season, and reunited him with former Thunder teammate James Harden, whom had played for the team from the 2009 to 2012 seasons.