The Olympic Oath is taken by one athlete and one judge at the opening ceremonies of each Olympic Games.

The verse of the oath taken by the Athlete is as follows:

In the name of all the competitors I promise that we shall take part in these Olympic Games, respecting and abiding by the rules which govern them, committing ourselves to a sport without doping and without drugs, in the true spirit of sportsmanship, for the glory of sport and the honour of our teams

The judge takes a slightly different oath like:

In the name of all the judges and officials, I promise that we shall officiate in these Olympic Games with complete impartiality, respecting and abiding by the rules which govern them in the true spirit of sportsmanship

A call for an oath was announced as early as 1906 by International Olympic Committee (IOC) president and founder Pierre de Coubertin in the Revue Olympique (Olympic Review in (French)). This was done in an effort to ensure fairness and impartiality.

The Olympic Oath was first taken at the 1920 Summer Olympics in Antwerp by a fencer/water polo player. The first judge's oath was taken at the 1972 Winter Olympics in Sapporo.

The athletes and officials who took the Olympic oath for the last ten years are
1996 Summer Olympics Teresa Edwards / Hobie Billingsley
1998 Winter Olympics Kenji Ogiwara / Junko Hiramatsu
2000 Summer Olympics Rechelle Hawkes / Peter Kerr
2002 Winter Olympics Jimmy SheaAllen / Church
2004 Summer Olympics Zoi Dimoschaki / Lazaros Voreadis
2006 Winter Olympics Giorgio Rocca / Fabio Bianchetti

Source: Wikipedia