The Belgian international has entered a fresh deal that will keep him at Old Trafford until 2020, with the option of a further year.
Fellaini has been linked with a number of clubs this season. Gambling.com's new tool, The Transfer Hound, recognised him as one of the transfer stories of the summer, but that now looks to be over after he committed his future to United.
"I am pleased to be continuing my journey as a Manchester United player. I made this decision because I am very happy here," Fellaini told United's official website.
"I feel like this team, under Jose [Mourinho], still has a lot we want to achieve."
The former Everton midfielder has made 156 appearances for United since joining the club in 2013.