Norway international midfielder Havard Nordtveit has joined Hoffenheim from West Ham for an undisclosed fee, both clubs have announced.
Nordtveit, who is 26 on Wednesday, joined the Hammers on a free transfer from Borussia Monchengladbach last summer and now returns to the Bundesliga after a year in the Premier League.
A statement on whufc.com read: "Havard Nordtveit has completed a transfer to German Bundesliga side Hoffenheim for an undisclosed fee."
Nordtveit, who has signed a five-year deal until June 2022, made 21 appearances for the Hammers and described his year in England as "less than ideal".
He told Hoffenheim's official website, achtzehn99.de: "I obviously know the Bundesliga very well from my years at Gladbach and I'm convinced I will be able to make the impact that TSG are hoping for."
Nordtveit first played in Germany when he joined FC Nurnberg from Arsenal in 2009. He made 152 Bundesliga appearances for Borussia Monchengladbach before moving to the Hammers.
Hoffenheim director of football Alexander Rosen said: "He is much more than just a strong addition to our squad on a sporting level.
"Havard is also a big personality off the pitch. Without his willingness to make a personal financial sacrifice, this transfer would never have been possible."