Martial had a club option in his contract that would extend him for another season at Old Trafford.
Manchester United are believed to have triggered the 12-month extension in Anthony Martial's current contract to tie him to the club for another year until 2020.
Martial was due to be out of contract at the end of this season and could theoretically have started to discuss a potential pre-contract agreement with overseas clubs as soon as January. But United have prevented that from happening and remain intent on a longer-term deal.
Although not publicly announced by the club, the news about the Frenchman's contract emerged on Monday afternoon and was reported independently by BBC Sport, the Manchester Evening News and Evening Standard at around the same time.
This is a temporary measure and all three outlets note that further talks are still ongoing.
Martial, who recently celebrated his 23rd birthday, appears to have overcome his personal difficulties with manager Jose Mourinho and has returned to something like his best form of old over the last couple of months.
Emerging as a rare bright spark in an otherwise underperforming side, the player is United's top scorer with eight goals so far this season. His impact was severely missed against Liverpool on Sunday when a minor injury complaint saw him limited to the role of a late substitute.
United fans will hope to see Martial restored to the starting lineup on Saturday when a trip to relegation threatened Cardiff is on the schedule to kick off the busy festive period.
United also face Huddersfield, Bournemouth and Newcastle in the Premier League over the next two weeks, before hosting Reading at Old Trafford in the FA Cup third round on 5 January.