Charlize Theron joked she is in a ''thruple'' with Nicole Kidman and Margot Robbie.

The trio star in 'Bombshell', the real-life story of the women of Fox News who accused former network chairman and CEO Roger Ailes of sexual harassment, and Charlize quipped that they all became so close they are now in a relationship with each other.

After calling Margot and Nicole her ''girl-crushes'', she added that they were all in a ''thruple''.

Nicole later joked to Entertainment Tonight: ''Oh yeah, I knew. It's been going on for so long. We're the best secret keepers in the world. Threesome, yeah!''

Meanwhile, Nicole praised Charlize for getting the film made.

She said: ''This film is a very powerful film... and Charlize really sort of championed getting it made. So when Margot and I came in, we went, 'Yeah, of course, we want to be there, we want to support you. We want to get this thing made.'''

Kidman, 52, stars as Gretchen Carlson and Charlize, 44, plays Megyn Kelly, while Margot, 29, stars as a composite character named Kayla Pospisil.

And Nicole said she feels lucky to be able to make movies like this, which cover important topics.

She said: ''I feel fortunate, and I just always try to go back to the work. I seek out the filmmakers I want to work with, and the people I want to work with. Take care of my children, be a good wife. Just trying to always balance. I'm just trying to do my best, which most women in the world are doing.''