Ghostbusters star Leslie Jones says she feels like she is in her own "personal hell" after receiving racist messages on Twitter.
The 48-year-old says she has been sent tweets blaming her for Aids and comparing her to a gorilla.
The actress has accused the site of not doing enough to deal with online trolls and is taking a "break" from it.
Twitter has admitted "a lot of work" is needed to improve how it handles the problem.
Leslie Jones is in the remake of the hit 1980s film Ghostbusters, which was released in the UK on Friday.
The decision to cast all females has been criticised by some Ghostbusters fans.
The movie's trailer has attracted more than 900,000 "dislikes" on YouTube so far. That's a record.
On Monday, the actress started sharing offensive messages she had received so far.
Over the hours, her tweets became more frequent as she became increasingly upset and frustrated.
She called those responsible "ignorant children", "crazy" and "sick", and at one point wrote, "it shouldn't be like this".
At one point the Saturday Night Live star said that she now understands why some celebrities do not have Twitter accounts and accused the site of not doing enough to protect its users.
A short time later, Twitter's CEO Jack Dorsey sent her a reply, asking her to "DM" him.
Leslie also became increasingly angry with people who told her to "ignore it".
"Stop letting the ignorant people be the loud ones," she wrote. "We have to make people take responsibility for the hate they spew. We have to stand up to it."
#LoveForLeslieJ soon began trending, while stars like Ghostbusters director Paul Feig leapt to her defence.
Leslie has previously spoken about quitting the site, and after this incident wrote that she would take a "break" from it, though did not specify for how long.
Her final tweet said: "I leave Twitter tonight with tears and a very sad heart. All [of] this cause I did a movie. You can hate the movie but the (abuse) I got today... Wrong."
A spokesman for Twitter has said "its taken action on many of the accounts reported to us by both Leslie and others" but that it relies on people to report this type of behaviour.
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