The 31-year-old Girls actress, writer and producer and 33-year-old Bleachers musician broke up in December, a source tells E! News exclusively, although their reps are yet to go public with the news.
“It was mutual,” the source told E!. “Jack and Lena were growing apart and it just made sense for them to end their relationship where it was.”
But as recently as November, Dunham tweeted that she thought she’d overheard Antonoff planning a proposal, Page Six reports.
Both had spoken publicly about their future together, and had revealed a pact not to get married until gay marriage was legalised in the US.
They met when they were set up on a blind date in 2012.