Serena Williams will return to the Washington Kastles in the 40th season of World Team Tennis.

WTT announced Monday that Williams will play for the defending champion Kastles for the first time since 2011. The coed summer league co-founded by Billie Jean King starts July 12, with the Kastles and Williams traveling to Boston.

The top-ranked Williams will compete on the road July 20 against Philadelphia and at home July 21 in Washington. Venus Williams will play a home match July 14 for the Kastles, whose lineup includes Martina Hingis.

Eugenie Bouchard (Boston) returns, along with veterans John Isner (Springfield, Missouri) and Andy Roddick (Austin).

The conference championships begin July 30, with the finals Aug. 2.