Suspended by the club on Sunday.
Manchester United striker Mason Greenwood has been arrested after his girlfriend accused him of rape and physical abuse.
The allegations were released on social media on Sunday and included video, photographs, and a voice note claimed to be a conversation between Greenwood and the woman.
"Greater Manchester Police was made aware earlier today (Sunday January 30) of online social media images and videos posted by a woman reporting incidents of physical violence," Greater Manchester Police said in a statement.
"An investigation was launched and following enquiries we can confirm a man in his 20s has since been arrested on suspicion of rape and assault. He remains in custody for questioning. Enquiries are ongoing," the statement further read.
Earlier on Sunday, Manchester United had announced that Greenwood would not return to training or play any matches "until further notice" after he was accused.
Manchester United suspended Greenwood on Sunday, a move that followed accusations online that the 20-year-old player had assaulted a woman.
In an initial statement on Sunday, the club said it was "aware of images and allegations circulating on social media," saying it would not comment further until the facts had been established, and adding:
"Manchester United does not condone violence of any kind."
In a later statement, United said, "Mason Greenwood will not return to training or play matches until further notice."
Reuters was not immediately able to contact Greenwood or a representative for him. The BBC reported that Greenwood had not responded to the social media allegations.
Greater Manchester Police said a man was arrested on suspicion of rape and assault and was being held in custody for questioning after social media images and videos were posted by a woman reporting incidents of physical violence.
In keeping with police practice they did not name the suspect.
Greenwood has six goals and two assists in 24 matches in all competitions for United this season. He began his career at United's academy and has played once for the England national team.