Reece Oxford has joined Augsburg from West Ham on a four-year contract for an undisclosed fee.
The 20-year-old spent the second half of the 2018/19 campaign on loan at the Bundesliga club and made nine appearances in all competitions.
Oxford became West Ham's youngest player at 16 years and 198 days old after making his senior debut in a Europa League qualifying game in 2015.
The central defender, who can also operate as a holding midfielder, had spells with Reading and Borussia Mönchengladbach before joining Augsburg on loan in January 2019.
Negotiations reopened in July between FC Augsburg and West Ham after an initial deal for the England U20 international fell through.
Oxford, who made 17 first-team appearances for West Ham, did not travel to China for the Premier League Asia Trophy tournament.
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