The comedy is yet to enter its fifth season, which premieres in February, reported Variety.
The decision to end "Girls" after six seasons comes as a surprise as creator and star Dunham has commented on the ending of her show much in the past.
Along with Dunham, the show stars Allison Williams, Jemima Kirke, Zosia Mamet, Adam Driver,Alex Karpovsky and Andrew Rannells.
HBO is yet to make an official announcement on the ending of the show but Dunham had hinted in the past that she would want to end "Girls" at an appropriate time.