US actor Armie Hammer has been accused of raping a woman in Los Angeles in 2017.
The woman, a 24-year-old named only as Effie, made the allegations during a virtual news conference on Thursday.
Hammer, 34, denied the allegations. His lawyer said they were "outrageous" and Hammer "welcomes the opportunity to set the record straight".
Los Angeles police told the BBC Hammer was a suspect in a sexual assault investigation opened on 3 February.
The accuser broke down while reading a prepared statement about the allegations against Hammer, known for films including The Social Network and Call Me By Your Name.
She spoke alongside high-profile women's rights lawyer Gloria Allred, alleging she first met Hammer on Facebook in 2016, when she was 20.
"I fell in love with him instantly," she said.
The women alleged that, as the relationship progressed, Hammer used "manipulation tactics in order to exert control over me".
She said he would "test my devotion to him, finally removing and crossing my boundaries as he became increasingly more violent".
The woman accused the actor of abusing her "mentally, emotionally and sexually".
She said the alleged rape happened on 24 April, 2017.
She said: "Armie Hammer raped me for over four hours in Los Angeles, during which he repeatedly slapped my head against a wall, bruising my face.
"During those four hours, I tried to get away and he wouldn't let me. I thought that he was going to kill me.
"He then left with no concern for my wellbeing. I was completely in shock and I couldn't believe that someone I loved did that to me."
She said she was left suicidal by the alleged rape, adding she felt "immense guilt" at not speaking out sooner.