The Celtics were valued at $4.7 billion last October by Forbes magazine, having leaped 18% in value to rank behind only the Golden State Warriors ($7.7 billion), New York Knicks ($6.6 billion) and Los Angeles Lakers ($6.4 billion).
Wyc Grousbeck led a group that bought the Celtics in 2002 for $360 million.
But NBA clubs have sold for much bigger sums in recent months, with the Phoenix Suns going to Mat Ishbia in February 2023 for $4 billion and a co-ownership stake in the Milwaukee Bucks going to Jimmy and Dee Haslam for $3.5 billion last year.
The Dallas Mavericks, who lost to Boston in last month's NBA Finals, were sold last December with casino moguls Miriam Adelson and Patrick Dumont purchasing a 69% majority stake in the club for $3.8 billion.
"Boston Basketball Partners LLC, the ownership group of the Boston Celtics, announced today its intension to sell all the shares of the team," Celtics ownership said in a statement.
"The controlling family of the ownership group, after considerable thought and internal discussion, has decided to sell the team for estate and family planning considerations.
"The managing board of the ownership group expects to sell a majority interest in 2024 or early 2025 with the balance closing in 2028."
Grousbeck is expected to remain the team's representative on the NBA Board of Governors until the final sale completion in 2028, the ownership said.
Under the current owners, the Celtics won the NBA title in 2008, beating the Los Angeles Lakers, lost the final to Lakers in 2010 and dropped the 2022 final to Golden State before claiming this year's crown.
