Sporting Lisbon and Oguchi Onyewu have mutually agreed to end the American defender's contract, the club announced Friday.
Onyewu was a regular for Sporting during the 2011-12 season but was loaned to Malaga the following year.
He is now a free agent.
Onyewu played for the U.S. national team in the 2006 and 2010 World Cups and last appeared with the U.S. in July during the Gold Cup. He was not included in Jurgen Klinsmann's squad for September's World Cup qualifiers.