Spain 40 times crowned De Gea, helped United win the Premier League title in 2012-13, the FA Cup three seasons, the League Cup and the Europa League in 2016-17.
De Gea who has consistently been linked with a move to Real Madrid in recent seasons, was in the last year of his contract and would have been able to open talks with clubs outside England over a possible move in January.
In June 2011, Sir Alex Ferguson brought De Gea into Manchester United from Atletico Madrid in an £18.9m deal, since then he has made 367 united appearances.
The Spaniard came close to joining real in a £29m move in September 2015, but the deal collapsed because the necessary paperwork was not submitted in time on the final day of the transfer window.
When asked how he feels signing with united again,
“Now my future is fixed, all I want is to help this team achieve what I believe we can and win trophies again, together,”
“It has been a privilege to spend eight years at this great club.” De Gea replied.
United boss Ole Gunnar Solskjaer said: “I am delighted that David has committed his long-term future to the club.
“Over recent years, David has proved himself to be the best in the world and a vital part of our plans as we look to take Manchester United back to where it belongs.”
The Norwegian added that De Gea “represents everything you want in a goalkeeper”.