The Portuguese has become an irreplaceable player for United within 12 months of arriving from Sporting CP.
While Fernandes has been the most productive player in the Premier League since signing, he still has a lot to achieve at United.
"Definitely not the result I wanted to celebrate my first year as a Red, but we'll keep working to improve," he said in a social media post.
"It's an absolute honour to play football with the Man Utd badge on my chest.
"The history of this football club was built over wins, many wins. I came here to help on continuing that legacy, and I won't rest until I do it.
"I want to thank all the fans for your outstanding support. Hopefully, this was only the first of many years together.
"Glory, glory Man United!"