2023–24 Boston Celtics season

The 2023–24 Boston Celtics season is the franchise's 78th season in the National Basketball Association (NBA). After the Pittsburgh Penguins of the National Hockey League (NHL) missed the playoffs for the first time in 16 years, the Celtics entered the season in second place behind the Los Angeles Dodgers of Major League Baseball (MLB) for the longest active playoffs streak in major North American sports, at nine years (having last missed the playoffs in 2014).

This was the Celtics' first season without veteran Celtic and point guard Marcus Smart since 2013. In June 2023, Smart was traded to the Memphis Grizzlies in a three-team trade to acquire forward Kristaps Porziņģis of the Washington Wizards. On October 1, 2023, the Celtics sent guard Malcolm Brogdon, center/forward Robert Williams III, a protected 2024 first-round pick (acquired from the Golden State Warriors), and an unprotected 2029 first-round pick to the Portland Trail Blazers in exchange for 2-time All-Star guard Jrue Holiday of the Milwaukee Bucks. On March 14, 2024, the Celtics became the first team to clinch a playoff berth with their 117–107 win over the Phoenix Suns and the Philadelphia 76ers’ 114–105 loss to the Milwaukee Bucks. Six days later, on March 20, the Celtics won the Atlantic Division championship for the third straight season in a row following a 122–119 win over the Milwaukee Bucks during a 7-game winning streak. Three days after clinching the Atlantic Division, the Celtics defeated the Chicago Bulls. As a result, they clinched the #1 seed in the Eastern Conference for the first time since 2017.

On April 3, 2024, the Celtics defeated the Oklahoma City Thunder with a 135–100 win, clinching the best record in the NBA and securing a home-court advantage throughout the entire playoffs for the first time since 2008. It was also the first time the Celtics went on to win 60 or more regular season games since 2009.