Has any Olympian ever competed for two different countries in the same Olympics?

Answer 1

Quite a few athletes have competed in both the summer and winter Olympics, but only three have received medals in both. Those three are:

Eddie Eagan, United States 1932, Winter Bobsled, four-man Gold 1920, Summer Boxing, light heavyweight Gold Jacob Tullin Thams, Norway 1924, Winter Ski jumping, large hill Gold 1936, Summer Yachting, 8-meter Silver Christa Luding-Rothensburger, East Germany 1984, Winter Speed skating, 500m Gold 1988, Winter Speed skating, 1,000m ; 500m Gold, Silver 1988, Summer Cycling, 1,000m Silver

Answer 2

The IOC rules are:

Athletes with dual nationality may compete for the country of their choice.

However, if they have already represented one country either at the Games or another major sports event, they may not compete for a different country before a period of three years has elapsed.

So no, not in the same Olympics, but someone may compete for two different countries in two separate Olympics.

No idea if anyone ever has...