The highly-rated 17-year-olds have already established themselves as first-team regulars at United and are being monitored by a number of major clubs.
Premier League strugglers Sunderland have had bids rejected for central defender Souttar, who has also been linked with Everton.
But he has now signed a new deal committing him to Dundee United until the end of the 2015/16 season along with midfielder Gauld, who has made 25 senior appearances and has reportedly been watched by scouts from Real Madrid.
Meanwhile, midfielder and Scotland U19 captain Darren Petrie has extended his deal with the Scottish Premiership side until May 2015, while 16-year-old full-back Euan Spark has signed until May 2016.
United manager Jackie McNamara said: "This is very positive news for the club and its fans. These four lads demonstrate exactly what we are trying to achieve at Dundee United.
"Ryan and John have already made the step up into the first-team squad and Euan and Darren have both experienced being with the first team.
"Ryan and John have shown they see their future at the club and indicated a determination to continue their football education at Tannadice.
"They have made great progression in their young careers so far and developing in the Scottish Premiership with United is the best option for that to continue."