De Gea is under fresh pressure this season with the addition of Dean Henderson.
"I've been here for many years now," said the Spaniard.
"I have a lot of experience and I think I have kept a high level for a long time now.
"I have the trust of the manager, the club and my teammates. I'm happy to be here and I look forward to several years here. Hopefully good things will happen with this club, like titles, and I hope I can remain number one here for a long time to come."