The 17-year-olds are first-team regulars and have attracted the interest of several major clubs.
United recently received bids from Sunderland for centre-back Souttar and reports on Monday claimed he was a target for Everton.
But Souttar, who has made 17 appearances for United's first team, has committed himself to the club until May 2016.
Creative midfielder Gauld has netted four goals in 25 games for United and was reportedly watched by Real Madrid scouts this season. He has also signed a deal until May 2016.
Meanwhile, holding midfielder and Scotland Under-19 captain Darren Petrie, 18, who made his first-team debut in January and was recently on loan at Brechin, has signed until May 2015 while 16-year-old full-back Euan Spark has penned a deal 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."