Rafael said goodbye to the United faithful via Instagram after he completed his medical with the Ligue-1 club on Monday, leaving the Red Devils following eight years at Old Trafford.
The Brazil international struggled for form and fitness for much of the previous campaign, which saw him limited to playing in the reserves and the Under-21 squad.
And the signing of Matteo Darmian from Torino has pushed Rafael even further down the pecking order, with manager Louis van Gaal also insisting the Antonio Valencia is his first choice right back.
The defender then took to Instagram to bid his farewell, in which he stated: “I want to thank Manchester United fans for all the love during those 8 years.
“Since I signed with the club I lived incredible moments, after all it was 8 years wearing the shirt of one of the biggest clubs of the world.
“Thank you United Kingdom, I learned a lot in this country, as a player, and no doubt as a human being, lessons that I will keep for the rest of my life.
“Thank you Sir Alex Ferguson for always believing in my work and for all the doors that you opened up to me. Now it’s a new path, a new challenge, God bless me!”
The 25-year-old arrived at Manchester from Fluminense along with his twin brother Fabio back in January 2009, going on to play over 150 games for the 13-time Premier League champions.