Title: History of the Boston Celtics
Content:  The Boston Celtics are an American professional basketball team based in Boston. Founded in 1946 as a charter member of the Basketball Association of America, the Celtics then moved into the National Basketball Association (NBA) in 1949, as said league was formed by the merger of the BAA merged with the National Basketball League. Currently playing in the Atlantic Division of the Eastern Conference, the Celtics have the most NBA titles with 17 championships. Eleven of those occurred between 1957 and 1969, with a dynasty led by center Bill Russell and coach/general manager Red Auerbach. The Celtics won two more titles in the 1970s under coach Tom Heinsohn, and three more in the 1980s under the leadership of forward Larry Bird. After a 22-year drought, the Celtics got their latest title in 2008.
Title: History of the Boston Celtics
Content:  The teams split the first four games, and after the Celtics won Game 5 in Milwaukee they headed back to Boston leading three games to two, with a chance to claim the title on their home court. However, the Bucks won Game 6 when Kareem Abdul-Jabbar nestled in a hook shot with three seconds left in the game's second overtime, and the series returned to Milwaukee. But Cowens was the hero in Game 7, scoring 28 points, as the Celtics brought the title back to Boston for the first time in five years. In 1976, the team won yet another championship, defeating the Phoenix Suns in 6 games. The Celtics advanced to the 1976 NBA Finals, which featured one of the greatest games in the history of the NBA. With 
Title: Boston Celtics
Content:  With Bill Russell, the Celtics advanced to the 1957 NBA Finals and defeated the St. Louis Hawks in seven games, the first of a record 17 championships. Russell went on to win 11 championships, making him the most decorated player in NBA history. In 1958, the Celtics again advanced to the NBA Finals, this time losing to the Hawks in 6 games. However, with the acquisition of K.C. Jones that year, the Celtics began a dynasty that would last for more than a decade. In 1959, the Celtics won the NBA Championship after sweeping the Minneapolis Lakers, the first of their record eight consecutive championships. During that time, the Celtics met the 
Title: NBA Finals
Content:  only eight years of existence as a franchise, overcame a losing record early in the season to build a remarkable win streak to finish 42–40. They achieved upset victories over the Seattle SuperSonics and the Warriors, before facing Boston in the Finals. The teams split the first four games, before Game 5 went into three overtimes and Boston won 128–126. The Celtics quickly managed to secure their 13th championship, defeating the Suns 87–80 in Game 6. Other franchises that won their first titles in the 1970s included the Portland Trail Blazers in 1977, and the Washington Bullets, who defeated the SuperSonics in 1978. The SuperSonics managed to exact revenge on the Bullets the following season, as they won their first title in 1979.
Title: History of the Boston Celtics
Content:  Russell joined the Celtics in December 1956 and went on to play most every game during which the Celtics advanced to the NBA Finals and defeated the St. Louis Hawks in seven games, giving the Celtics the first of their record 17 NBA Championships. In 1958, the Celtics again advanced to the NBA Finals, this time losing to the Hawks in 6 games. However, with the acquisition of K.C. Jones that year, the Celtics began a dynasty that would last for more than a decade. In 1959, with Cousy at point guard, Russell at center and Heinsohn at forward, the Celtics won the 
Title: 1986–87 Boston Celtics season
Content:  The 1986–87 Boston Celtics season was the 41st season of the Boston Celtics in the National Basketball Association (NBA). The Celtics entered the season as the defending NBA Champions, having defeated the Houston Rockets in the 1986 NBA Finals in six games, winning their sixteenth NBA championship. In the playoffs, the Celtics swept the Chicago Bulls in the First Round in three games, defeated the Milwaukee Bucks in the Semi-finals in seven games, and the Detroit Pistons in the Conference Finals in seven games to reach the NBA Finals for the fifth time in the 1980s. In the Finals, the Celtics faced off against their long time rival, the Los Angeles Lakers, in their third and final matchup in the NBA Finals in the 1980s. The Celtics would lose in six games to the Lakers, and it marked the last time the Celtics made it to the NBA Finals until 2008. Remarkably, the 1987 NBA Finals was the first playoff series for the Celtics in the Bird era in which they did not have the home court advantage, as they had played 24 consecutive series with the home court advantage starting in 1980.
Title: Boston Celtics
Content:  NBA titles in 1974 and 1976. The Celtics again returned to dominance in the 1980s. Led by the "Big Three" that featured Larry Bird, Kevin McHale, and Robert Parish, the Celtics won the 1981, 1984, and 1986 championships. 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. The Celtics returned to the NBA Finals in 2010, only to lose to the Lakers in a 
Title: 1983–84 Boston Celtics season
Content:  The 1983–84 Boston Celtics were champions of the National Basketball Association (NBA) led by regular season and finals MVP Larry Bird. In the playoffs, the Celtics defeated the Washington Bullets in the First Round in three games, defeated the New York Knicks in the Semi-finals in seven games, and defeated the Milwaukee Bucks in the Conference Finals in five games, advancing to the NBA Finals. In the Finals, the Celtics faced their long time rival, the Los Angeles Lakers, the first time the two teams faced off against each other since 1969 in which the Celtics won 4–3, and the first time the two teams met in the Finals in the 1980s. The Celtics would go on to defeat the Lakers in seven games, winning their fifteenth NBA championship, and extending their NBA Finals victories over the Lakers to 8.
Title: History of the Boston Celtics
Content:  1980s. However, that year the Celtics' string of NBA titles was broken as they lost to the Philadelphia 76ers in the Eastern Conference Finals. The aging team managed two more championships in 1968 and 1969, defeating the Lakers each time in the NBA Finals. Russell retired after the 1969 season, effectively ending a dominant Celtics dynasty that had garnered 11 NBA titles in 13 seasons. The streak of 8 consecutive NBA championships is the longest streak of consecutive championships in U.S. professional sports history. Other important players during this era included Sam Jones, John Havlicek, Bill Sharman, Frank Ramsey, and Satch Sanders.
Title: History of the Boston Celtics
Content:  salvaged by the trade, the Celtics went on to win 49 games. The 49 victories were the franchises most since 1992, when Larry Bird was still playing, and the Celtics made the playoffs for the first time since 1995. The Celtics won a hard-fought five game series with the 76ers in the first round, 3 games to 2. Pierce scored 46 points in the series-clinching blowout at the Fleet Center. In the conference semifinals the Celtics defeated the favored Detroit Pistons 4 games to 1 in a series best remembered for the Celtics low-scoring (66–64) game 3 victory. In their first trip to the Eastern Conference Finals since 1988, 

Question: when did celtics win the championship?
Answer: 1969 NBA Finals.