The 37-year-old was released from his contract by mutual consent on Tuesday, two days before Portugal kick-off their World Cup campaign against Ghana.
After only four Premier League starts during the first half of the season, Ronaldo made a series of explosive comments to Piers Morgan during an interview with Talk TV.
Ronaldo accused United of “betrayal” and claimed he did not respect manager Erik ten Hag.
It is an unhappy end to a relationship stretching back to 2003. In his first spell running until 2009, Ronaldo won three Premier League titles and the Champions League before returning in 2021.
Despite 24 goals in all competitions last season, Ronaldo missed preseason – the first under ten Hag – and has since been forced to watch most of the action from the sidelines.
A statement from Ronaldo read: “Following talks with Manchester United, we’ve mutually agreed to end our contract.
“I love Manchester United and I love the fans, that will never ever change. It feels like the right time to seek a new challenge. I wish Man Utd all the best”.