Lena Dunham has revealed that she cheated on music producer Jack Antonoff during their five-year relationship, whilst she had suspicions about his close relationship with ‘a teen pop star’.

The actress, now 39, opened up about her tumultuous relationship with Taylor Swift’s writing partner, 42, in her new memoir, Famesick, released on Tuesday.

Dunham wrote that she and Antonoff had their ‘worst-ever fight’ after her hysterectomy surgery in November 2017, which resulted in a rehab stint for her addiction to post-surgery pain medication/ She and Antonoff then paused their relationship as she went on tour.

She explained that during this time, she ended up reconnecting with a childhood friend and ex named Nick, but admitted she should have been paying closer attention to Antonoff, who had been spending extended time in the studio with a ‘teen pop star.’

For years, rumors had been swirling that Antonoff was involved romantically with  Lorde, but the two have always denied they have had a romantic relationship.

Dunham wrote how ‘up until now, I had seen myself as some kind of half wife, and so I had observed wifely code but the events of the past few weeks had changed the game, and it was every woman for herself, just trying to survive.’ 

Things escalated as the actress went on a date and took a cab back to Nick’s apartment, where she wrote that she told Nick: ‘I’ve been through something awful. I don’t want to talk about it, but I need you to f*** me and I need you to do all the work.’

The two continued sleeping together for two weeks while Antonoff was on tour and they even got ‘engaged’ after her split from the musician but ultimately ended up breaking up after Dunham’s rehab stint in 2018.

Dunham also addressed infidelity rumors from Antonoff’s side, revealing that her partner had been spending time in the studio with someone she only refers to as a ‘teen pop star.’

She even wrote that the star was ‘weeping into Jack’s lap’ when she came home one day. 

Lena explained that whilst she ‘flirted’ with others during their relationship ‘I had observed careful boundaries, never taking it far enough that I could be declared out of bounds.’

‘If I’d wanted to look, perhaps I may have seen that Jack was not observing them as closely as I was. I wasn’t paying attention, but the internet sure was, and they made some pretty amazing PowerPoints on the issue, so convincing they had me rethinking events that I myself had been present for.’

While all the parties have denied speculation that Antonoff cheated on Dunham with Lorde, some dedicated fans are still convinced something happened, with one even creating the aforementioned PowerPoint to make their case.

The document – which insisted that Lorde’s album Melodrama (produced by Antonoff and recorded largely in the apartment-dash-studio he shared with Dunham) offered an insight into the alleged ‘affair’ – went viral.

In a series of rambles, it posited that Lorde and Antonoff got together in April 2016, just months before Jack and Dunham’s split in December 2017, after five years of dating.

The slides also included a ‘timeline’, stating that Lorde and Antonoff met sometime around 2014 to 2015, whereas Antonoff and Dunham are understood to have started their relationship around 2012.

It summarized reports made in January 2018, which claimed that Antonoff was ‘seeing someone else’, as per US Weekly – as well as the follow-up that just one month later, he and Lorde were spotted looking cozy and hugging while strolling in her native Auckland, where his band was opening for Paramore. 

Speaking to The Cut in 2018, Dunham praised user @buzzkillary, who was behind the project.

 ‘Actually, I completely respect this girl, because she did a very good job and she was very funny,’ she quipped – albeit admitting that ‘it was so embarrassing’.

‘It was awful because I felt like a weird… I don’t think anything happened between them. I can never know someone else’s life. I have never spoken to Ella [Lorde] about it,’ she continued.

‘We haven’t talked since Jack and I broke up. It was awful, and I couldn’t do anything about it except trust that what he was saying to me was true.’

Antonoff and Lorde, meanwhile, have both rubbished rumors that anything romantic between them ever happened, both taking to social media that same year.

‘Normally I would never address rumors but I resent having the most important friendships and working relationships in my life reduced to dumb hetero normative gossip,’ the producer penned.

‘Those relationships are deeply important and sacred. With that said, I’m not seeing anyone. lol.’

‘Guys… Jack and I are not dating, for the last time,’ Lorde also wrote on X. ‘I love him, he’s awesome, but we’re not dating! Please!’

In July 2021, Lorde went so far as to tell Ash London Live on Australia’s Hit Network that she sees him as a ‘platonic husband’.   

‘Jack’s and my relationship is really deep and is like a marriage in some ways – a platonic marriage,’ she explained.

‘We’re in it for life I think at this point. We’ve been very close for five or six years now. We don’t seem to get sick of each other. But who knows, anything could happen.’   

Lorde set the record straight once again, a few months later, in an interview with The New York Times.

She had hit back at the ‘growing narrative’ concerning her connection with Antonoff following his involvement in her album Solar Power that year.

The singer, whose real name is Ella Marija Lani Yelich-O’Connor, said it was ‘insulting’ and ‘sexist’ for critics to refer to Solar Power as ‘a Jack Antonoff record’.

‘I haven’t made a Jack Antonoff record. I’ve made a Lorde record and he’s helped me make it and very much deferred to me on production and arrangement,’ she added. 

‘Jack would agree with this. To give him that amount of credit is frankly insulting.’ 

Lorde then criticized the speculation surrounding her personal relationship with Antonoff, as well as the idea she’s part of his so-called ‘stable’ of female collaborators.

She called the discussion around the subject, which has also included speculation about the pair’s romantic and sexual life, ‘retro’ and ‘sexist’.

Needless to say, all seems to be history – as Antonoff married actress Margaret Qualley in 2023, while Dunham wed musician Luis Felber in 2021.

• Famesick: A Memoir is on bookshelves and on sale at online book retailers now.