Left-back becomes fourth summer signing.
Sunderland have completed the signing of left-back Patrick van Aanholt from Chelsea.
The Dutch international has joined the Black Cats on a four-year deal, for an undisclosed fee.
The 23-year-old gained Champions League experience while with the Blues and has spent the last two seasons on loan with Dutch side Vitesse, where he also played in the UEFA Europa League.
Capped twice by his country at senior level so far, he was named in Louis van Gaal’s 30-man provisional squad ahead of the 2014 FIFA World Cup.
The player becomes the Black Cats’ fourth summer signing, following the arrivals of Billy Jones, Costel Pantilimon and Jordi Gomez.