Patrice Bergeron and Glen Murray were named assistant captains.
Chara, 29, a key free-agent signing by the Bruins last summer, becomes the third Slovakian-born player to wear a captain's C for an NHL team. Peter Stastny was captain of the Quebec Nordiques from 1975 to 1980 and Stan Mikita was a co-captain of the Chicago Blackhawks with Pit Martin from 1975 to 1977.
"Zdeno's leadership qualities have been apparent from the time he joined players for their informal skates prior to training camp," GM Peter Chiarelli said in making the announcement Tuesday. "He leads by example, both on and off of the ice, and he has earned the respect of everyone in our dressing room.
"He recognizes the leadership abilities of his two assistant captains as well as other players, and he also realizes that every player has strengths that they bring to our team and that bringing those strengths together is crucial to our success."
Boston had been without a captain since trading Joe Thornton last Nov. 30.
Chara, a defenceman who at six-foot-nine is the NHL's tallest player, joins such great Bruins as John Bucyk, Dit Clapper, Milt Schmidt, Cooney Weiland, Terry O'Reilly and Ray Bourque on the club's all-time captain's roster.
Chara is entering his ninth NHL season, his first with the Bruins since leaving the Ottawa Senators as an unrestricted free agent July 1.
Chara was named to the NHL's first all-star team and was a Norris Trophy finalist in 2003-04. He was named to the second all-star team and finished fourth in Norris voting in 2005-06.
His career NHL totals are 57 goals and 118 assists for 175 points and 901 penalty minutes in 530 games.
Note: The Ottawa Senators named defenceman Chris Phillips their assistant captain Tuesday. Daniel Alfredsson is the team's captain while Wade Redden is the other assistant.