Serena Williams
French Open champion Serena Williams out after shock second round victory.

Defending champion Serena Williams and sister Venus have both been eliminated at the second round stage of the French Open.

Serena's defence of her title at Roland Garros was brought to a shuddering halt by Spain's 20-year-old Garbine Muguruza, who shook the women's draw with a 6-2 6-2 victory.

Venus meanwhile was deprived of possible third round match against her sister after succumbing to a 2-6 6-3 6-4 defeat to Slovakian teenager Anna Schmiedlova, seeded 58th.

Williams' exit marks the first time the top two seeds in the women's draw have been elimnated from any grand slam before the third round.

Venezuelan-born Muguraza took the first set 6-2 after the defending champion returned long before storming into a three game lead to stun the defending champion. A frustrated Serena clawed one game but was soon broken again after two double faults, before slamming a forehand wide as her opponent edged towards a shock victory.

Serena responded with three break back points in the sixth game of the set but Muguraza's persistent targeting of the reigning champions' floundering backhand forced the game to deuce. In yet another error the American netted her return to leave her trailing 5-1.

Muguraza edged ever closer to victory with a powerful serve down the line before sealing the 6-2 6-2 victory against the top seed.

Venus was deprived of her place in the third after defeat to Slovakian teenager Schmiedlova, seeded 58th, in the French capital.

The seven time grand slam champion took the opening set and followed up with an early break in the second but the 19-year-old responded in scintillating fashion, taking eight of nine games to eliminate 29th seeded Venus.