The Boston Celtics are an American professional basketball team based in Boston, Massachusetts. The Celtics compete in the National Basketball Association (NBA) as a member of the league's Eastern Conference Atlantic Division. Founded in 1946 as one of the league's original eight teams, the team play their home games at TD Garden, which they share with the National Hockey League (NHL)'s Boston Bruins. The Celtics are one of the most successful teams in NBA history; the franchise has won the most championships in the NBA with 17, accounting for 23.9 percent of all NBA championships since the league's founding.
The Celtics have a notable rivalry with the Los Angeles Lakers, and have played the Lakers a record 12 times in the NBA Finals (including their most recent appearances in 2008 and 2010), of which the Celtics have won nine. Four Celtics players (Bob Cousy, Bill Russell, Dave Cowens and Larry Bird) have won the NBA Most Valuable Player Award for an NBA record total of 10 MVP awards. Both the nickname "Celtics" and their mascot "Lucky the Leprechaun" are a nod to Boston's historically large Irish population.
After winning 16 championships throughout the 20th century, the Celtics, after struggling through the 1990s, rose again to win a championship in 2008 with the help of Kevin Garnett, Paul Pierce, and Ray Allen in what was known as the new "Big Three" era, following the original "Big Three" era that featured Larry Bird, Kevin McHale, and Robert Parish, which combined to win the 1981, 1984, and 1986 championships.
Following the win in 2008, general manager Danny Ainge began a rebuilding process with the help of head coach Brad Stevens, who led the Celtics to a return to the playoffs from 2015. During the following season, the Celtics clinched the top seed in the Eastern Conference, but were eliminated in the Conference Finals. This prompted an aggressive rebuild in 2017, where the team acquired All-Stars Kyrie Irving and Gordon Hayward. However, the pair struggled with injuries throughout the 2017–18 season, and the team was again defeated in the Eastern Conference Finals.