The 27-year-old Scottish international joined the club in 2000 and has become an important part of the English Premier League side's set up, making 288 appearances and scoring 21 goals.
"Darren has been at the club since he was 15," Ferguson said. "I am extremely proud that he came through the ranks of our youth academy and am delighted Darren has signed a new contract.
"He has developed into a top-class midfielder."
Fletcher has won three Premier League titles, the FA Cup, two League Cups, the Champions League and the FIFA Club World Cup during his time at United.
"I take great pride in playing for Manchester United," said Fletcher.
"I have won many trophies in my years playing here and I am looking forward to winning many more in the seasons to come."