Centre back Hobbs is no stranger to Tigers fans having spent the final three months of the 2010/11 season on loan at the KC Stadium.
The 22-year-old former Lincoln and Liverpool player impressed during 13 appearances to earn himself a permanent move.
Hobbs said: "I'm delighted now that it's all done and I'm finally a Hull City player. I am really looking forward to meeting up with the other lads for pre season and starting a push towards the Premier League.
"My time at the club last season only reinforced for me what a great club Hull City is - the fans, the stadium, the set up here, the manager and the players meant it was great to be a part of last season and I want to be part of it again."
Source: Team Talk
Source: Team Talk