West Ham bring in Hitzlsperger
"I am delighted to welcome Thomas to the club," chairman David Sullivan told the club website.
"He is the first of many signings this summer. We are going to sign a mixture of exciting young talent as well as the very best senior pros who can add real strength to the squad like Thomas."
The 28-year-old, who narrowly missed out on Germany's World Cup squad, is no stranger to England's top flight having played for Aston Villa before spells with VfB Stuttgart and most recently Lazio.
Hitzlsperger has signed a three-year-deal with the Upton Park club, who also appointed former Chelsea and Portsmouth boss Avram Grant as manager on Friday.