Alissa Violet — a popular YouTuber — has been arrested after she allegedly got into a ferocious argument with her boyfriend … TMZ has learned.

Sources tell TMZ … Alissa and Ryan Pownall went back to his apartment in Hollywood after a night out drinking at a local bar at the end of February.

When they got to the apartment, our sources say Alissa and Ryan — who were both allegedly intoxicated — got into an argument about Ryan’s phone.

Alissa left the apartment for a time, sources tell us, but later came back, and the argument continued … at which time, neighbors made a noise complaint to security. Later, the cops were called.

Law enforcement sources tell us … Alissa was ultimately arrested for making criminal threats … though they did not detail the nature of the threats.

Sources familiar with the incident told TMZ that Alissa may have had a knife in her hand — which would explain why she was arrested, but Alissa’s team has not confirmed or denied this allegation.

We’re told the pair — who dated for nine months — broke up after the incident.

Alissa is known as a lifestyle creator … sharing an inside look at her life filled with candid content, makeup tutorials, and more.