Williams, a seven-time grand slam champion, was beaten by 19 year old British teenager Laura Robson, who won 6-3, 6-2 in windy blistery conditions that made the conditions extremely difficult for both players.
Tennis - Former world no. 1 Venus Williams has exited the Italian Open in Rome in the first round on Monday.
Robson goes to to face Venus' sister Serena Williams, the world no 1, in the second round.
Robson is ranked no. 39 in the world while Venus is currently ranked no. 24. The 32 year old American has struggled with a lower back injury for much of this season and was seen clutching her back a few times in the match. Venus is also dealing with Sjorgen's Syndrome, which she was diagnosed with in 2011.
Laura Robson overcame strong winds to beat Venus Williams 6-3, 6-2 at the Italian Open on Monday and set up a second-round match with top-ranked Serena Williams.
Serena was in the stands to watch the match as she supported her sister and also scouted out her next opponent,
In other early first round matches, German Sabine Lisicki beat American qualifier Mallory Burdette 6-1, 6-2; local wild card Nastassja Burnett beat former world no. 11 Alize Cornet of France 6-2, 6-2.