Russell has become a first-team regular in recent months following loan spells at Forfar and Raith in previous seasons. The 20-year-old has made 25 appearances for United, netting five goals.
United manager Peter Houston told the club's official website: "I'm absolutely delighted that Johnny has agreed to extend his contract at Dundee United.
"He has made a big impression since breaking into the first team and I am now looking for him to continue the hard work to ensure he adds consistency to his game and continues to improve for the benefit of both himself and the club over the duration of this contract.
"It's great to see yet another young and improving player who wants to remain at the club longer term and once again, it shows the club's emphasis on nurturing and utilising its own youth system products."
Source: PA
Source: PA