Chris Smalling has signed a new contract with Manchester United, the Premier League club have confirmed.
Manager Louis van Gaal said he had rewarded the defender for his improved form this season with the agreement.
The 25-year-old's previous deal was due to expire in 2016 and United moved to avoid running the risk of losing him on a free transfer by ensuring he will stay at Old Trafford until 2019.
Van Gaal said on the club's official website: "Chris has improved and developed immensely during the short time that I have been at the club and has become an integral part of the first-team squad.
"He always conducts himself in a very professional manner and it is also pleasing that he has scored some important goals this season too. I am delighted he has signed a new contract."
Smalling added: "I'm delighted to sign my new contract. I am so proud to play for such a great club. We have developed as a team over the course of the season under Louis van Gaal and we are now playing as a complete unit.
"This is a very exciting time to be at Manchester United, we are all determined to get back to where we belong and competing at the highest level.
Former Maidstone centre-back Smalling joined United for £10.5 million from Fulham in 2010 and has gone on to make 147 appearances for the club, scoring nine goals, including four this season.
BREAKING: @ChrisSmalling has signed a new contract at #mufc which keeps him at the club until at least June 2019. pic.twitter.com/mlNYkHrb3v
- Manchester United (@ManUtd) April 21, 2015
After being an understudy to the established first-choice partnership of Nemanja Vidic and Rio Ferdinand for most of his first four seasons at Old Trafford, Smalling has formed a fine alliance with Phil Jones in the centre of the United defence in the recent wins over Tottenham, Liverpool and Manchester City.
Jones and fellow centre-back Jonny Evans are out of contract in 2016 and United are yet to resolve their futures.
Van Gaal is expected to sign another centre-back in the summer, with Borussia Dortmund's Mats Hummels the favourite to arrive, and the news that Smalling is staying could put Jones and Evans under more pressure.