Greenwood was released on bail last week after being questioned over the alleged rape and assault of a young woman.
The 20-year-old had been arrested after images and videos were posted online and, while in custody, he was further arrested on suspicion of sexual assault and threats to kill.
United have suspended Greenwood from playing or training with the club until further notice.
Nike last week issued a statement saying it was “deeply concerned by the disturbing allegations and will continue to closely monitor the situation”.
It has now confirmed Greenwood will no longer be endorsed by the company.
“Mason Greenwood is no longer a Nike athlete,” the firm said in a statement.
United have removed all Greenwood merchandise from their website, with his name absent from a drop-down list of players’ names for replica shirts.
A number of sponsors have reacted by distancing themselves from the player.
Greater Manchester Police did not name the footballer last week but said: “A 20-year-old man arrested on Sunday, January 30, 2022 on suspicion of the rape and assault of a woman has been released on bail pending further investigation.”
Greenwood, who made his United debut in 2019 after coming through the youth ranks, has played 129 times for the club, scoring 35 goals.
He signed a new deal in February 2021, keeping him at Old Trafford until at least 2025.
Greenwood made his England debut against Iceland in September 2020 but he and Manchester City midfielder Phil Foden were sent home after a breach of the team’s coronavirus guidelines.
He has yet to win another cap for the Three Lions.