Cittadini will be the third Italian at Wasps next season, where he joins international teammates Andrea Masi and Carlo Festuccia.
Cittadini, who showed his class against England in the final game of the RBS 6 Nations, is highly rated at international level and joins Wasps from Benetton Treviso.
Young said: “Lorenzo will be an excellent addition to our squad next year. I rate him as a very good prop at the highest level and his experience at international level will be a real boost for us.
“We’ve got some very good young props here at Wasps who will learn a lot from working with him. We want to build a squad which has strength in depth in every position and bringing in players like this will help us continue to build on that aim.”
Cittadini will join other new signings Bradley Davies, James Gaskell and Rob Miller at Wasps next season.