Defending champion Serena Williams was sensationally dumped out of the French Open on Wednesday in the biggest upset of the tournament so far.

The American 17-time grand slam champion and world No.1 slumped to a shocking 6-2 6-2 defeat at the hands of Spanish world No.35 Garbine Muguruza in just over an hour.

The defeat comes less than an hour after her sister Venus was also knocked out, this time by teenager Anna Schmiedlova of Slovakia 2-6 6-3 6-4.