The 22-year-old Spaniard, who joined up with his new teammates at the club's pre-season training camp in Mayrhofen on Sunday night, will wear the No13 shirt.
'The Bundesliga's a great league'
"I'm delighted we've been able to bring in a player of Oriol Romeu's international ilk," enthused Stuttgart head coach Armin Veh. "I've had my eyes on him for a while. Despite his age, he's already got experience playing in two of Europe's top leagues. I'm in no doubt that he'll be a big help here."
Romeu learned his craft in the youth ranks at FC Barcelona, before signing for Chelsea in August 2011. After winning the UEFA Europa League in 2012/13, he spent the 2013/14 campaign on loan at Valencia CF, penning a new three-year deal at his parent club earlier this summer.
"VfB really made an effort and the manner of the talks really pleased me," Romeu explained. "The Bundesliga's a great league that's getting better all the time. I'm looking forward to the challenge - being in a different country and getting to know new faces. It's great for my development."