Costel Pantilimon has joined Watford from Sunderland for an undisclosed fee.
The goalkeeper spent 18 months at the Stadium of Light following his transfer from Manchester City in July 2014, making 49 appearances for the Black Cats.
The Romania international has signed a three-and-a-half-year contract at Vicarage Road.
A statement on Sunderland's official website read: "Sunderland AFC would like to thank Costel and wish him the very best for the future at his new club."
Pantilimon has previous Premier League experience with Manchester City and has 20 caps at international level.