The Portugal international has contributed 49 goals and 39 assists in just 117 games for United.
Fernandes, who has already won the Sir Matt Busby Player of the Year award twice, has created more chances than any other United player since joining the club in January 2020.
The midfielder scored two goals for Portugal this week on his 42nd international appearance, against North Macedonia, as he helped to seal his country’s place at the 2022 FIFA World Cup.
Bruno Fernandes said: “From the moment that I joined Manchester United, I have had a special relationship with the club and our amazing fans.