what is gossip girl?
An American teen drama television series
Gossip Girl
Gossip Girl is an American teen drama television series based on the novel series of the same name written by Cecily von Ziegesar. The series, created by Josh Schwartz and Stephanie Savage, ran on The CW network for six seasons from September 19, 2007, to December 17, 2012.

what episode of gossip girl does blair and chuck get married In Season 6 -  In the series finale
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Gossip Girl [SEP] Introduction
She is reunited with her frenemy Blair Waldorf (Leighton Meester) and her mother Lily (Kelly Rutherford), and she also meets Dan Humphrey (Penn Badgley)—an aspiring writer from Brooklyn who is one of Serena's main love interests throughout the show. Other main characters include Nate Archibald (Chace Crawford), Chuck Bass (Ed Westwick), Jenny Humphrey (Taylor Momsen), Vanessa Abrams (Jessica Szohr), Rufus Humphrey (Matthew Settle) and Ivy Dickens (Kaylee DeFer). The success of "Gossip Girl" led to many adaptations outside the United States. The show received numerous award nominations and won 18 Teen Choice Awards. The CW officially renewed "Gossip Girl" for a sixth and final season on May 11, 2012.