Dennis Marvin Seidenberg (born 18 July 1981) is a German former professional ice hockey defenceman who played in the National Hockey League (NHL) for the Philadelphia Flyers, Phoenix Coyotes, Carolina Hurricanes, Florida Panthers, New York Islanders, and Boston Bruins, with whom he won the Stanley Cup in 2011.

After spending three years with Adler Mannheim of the Deutsche Eishockey Liga (DEL) in his native Germany, he signed with the Flyers in 2002.

[5] On 3 March 2010, Seidenberg and Matt Bartkowski were traded to the Boston Bruins for Byron Bitz, Craig Weller, and a second round draft pick.

Seidenberg drew attention for his outstanding play during the playoffs, at one point being cited as a potential Conn Smythe Trophy winner.

[12] At the conclusion of the 2015–16 season, Seidenberg's seven-year tenure with the Bruins ended, as he was bought out from the remaining two years of his contract on 30 June 2016.