The 33-year-old Witsel joined on a free transfer after his contract at Borussia Dortmund, which he joined in 2018, expired at the end of last season.
Witsel has a total of more than 600 appearances at club level _ including 77 in the Champions League _ and played at the last two World Cups with Belgium.
``I wanted to stay at a top level and Atletico is a top club,'' said Witsel, who will join fellow Belgium international Yannick Carrasco at the Spanish club.
Atletico said it acquired ``the services of a player with extensive experience,'' with Witsel having ``a great ability to dominate aerial play and to fight for the ball in the air with his opponents.''
Witsel will help to make up for the departure of Hector Herrera, who joined the Houston Dynamo in Major League Soccer.
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