In a statement on Twitter, Manchester United thanked Ronaldo for his "immense contribution across two spells at Old Trafford".
Ronaldo added: "Following conversations with Manchester United we have mutually agreed to end our contract early."
Sky's Rob Harris has the latest from Qatar.
See more on this story here: bit.ly/3i4tRcp
SUBSCRIBE to our YouTube channel for more videos: www.youtube.com/skynews
Follow us on Twitter: twitter.com/skynews
Like us on Facebook: www.facebook.com/skynews
Follow us on Instagram: www.instagram.com/skynews
For more content go to news.sky.com and download our apps:
Sky News videos are now available in Spanish here/Los video de Sky News están disponibles en español aquí www.youtube.com/channel/skynewsespanol