The 23-year-old Frenchman has made 162 appearances and scored 46 goals since making his debut for the club against Liverpool in September 2015.
“I am loving my time at this club,” said Martial. “From the day I joined I have been made to feel part of the United family and I have been incredibly humbled and overwhelmed by the warmth and love of our fans, who continue to amaze me with their support.
“I would like to thank (interim boss) Ole (Gunnar Solskjaer) and his coaching staff for their belief in me and for helping me to take my game to the next level. This club is all about winning trophies and I am sure the next piece of silverware is not that far away.”
Solskjaer said: “Anthony is one of those naturally gifted players that any coach would love to work with.
“For a young man, he has a good footballing brain which, when coupled with his exceptional talent, makes for a player with an exciting future ahead of him.”
The contract includes the option to extend for a further year.
For more news your way, download The Citizen’s app for iOS and Android.
Download our app and read this and other great stories on the move. Available for Android and iOS.