Citius Altius Fortius is the motto of what organisation

It is the Olympic motto
The Olympic motto is the hendiatris Citius, Altius, Fortius, which is Latin for "Faster, Higher, Stronger."

The motto was proposed by Pierre de Coubertin on the creation of the International Olympic Committee in 1894.

Coubertin borrowed it from his friend Henri Didon, a Dominican priest who was an athletics enthusiast.

Coubertin said "These three words represent a programme of moral beauty. The aesthetics of sport are intangible."

The motto was introduced in 1924 at the Olympic Games in Paris.

A more informal but well known motto, also introduced by Coubertin, is "The most important thing is not to win but to take part!" Coubertin got this motto from a sermon by the Bishop of Pennsylvania during the 1908 London Games.

Source:https://en.wikipedia.org/wiki/Olympic_symbols#Motto