Deadline reports that Dunham will write, direct and star in the currently untitled sitcom, which follows the lives of a group of girls in their early twenties.
Knocked Up director Apatow will executive produce the show alongside Dunham and Jenni Konner.
"Lena has a unique, truthful comic voice," he said. "I am excited to work with her and learn from her."
Konner added that she had become "obsessed with working with Lena".
"She has a staggeringly honest point of view and hilarious clear vision," she claimed.
Apatow's previous television output includes 1999 NBC sitcom Freaks and Geeks and Fox comedy Undeclared, which ran for one season between 2001 and 2002.