Actress Michelle Trachtenberg, known for a wide range of TV and film roles including in “Buffy the Vampire Slayer” and “Gossip Girl,” has died at the age of 39, sources told The Post.

Trachtenberg was found by her mother around 8 a.m. Wednesday at One Columbus Place, a 51-story luxury apartment complex in Manhattan’s Central Park South neighborhood, the sources said.

The actress recently underwent a liver transplant and died of natural causes, according to the sources.