Boston ? Paul Pierce, the Boston Celtics captain whose prolific but occasionally troubled career put him on the trading blocks last summer, signed a three-year, $59 million contract extension Monday that would keep him in Boston through the 2010-11 season.

“This represents a milestone for the Celtics and for Paul Pierce,” owner Wyc Grousbeck said. “Paul … has become a team leader on and off the court in the best Celtic tradition.”

Former Kansas University forward Pierce is scheduled to make about $31.5 million over the next two years, including a player option for 2007-08. The extension adds three years and $59 million after that.

A five-time All-Star, Pierce has played his entire, eight-year career with Boston and took over as co-captain in 2000. But his partnership with Antoine Walker failed to add to the team’s record cache of 16 NBA titles, and Pierce struggled in his role as elder statesman after he and Walker were split up.

During the 2005 playoffs, Pierce was ejected in a bizarre and, in his words, “boneheaded” move during Game 6 of their first-round playoff series against Indiana. But he put his troubles aside last season and averaged a career-high 26.8 points with 6.7 rebounds and 4.7 assists, equaling Larry Bird with his fourth straight 2,000-point season.

“Paul is one of the greatest Celtics in the history of our franchise,” basketball boss Danny Ainge said.

Pierce is the eighth-leading scorer in Celtics history. Last season, he led the team in scoring 63 times, in rebounds 26 times and in assists 31 times.

“The Celtics organization and the fans of Boston and New England have been great,” Pierce said. “And now we can continue to strive to put the 17th championship banner up in the rafters.”