The title International Grandmaster is awarded to superb chess players by the world chess organization FIDE. It is a lifetime title, in chess literature usually abbreviated as GM or IGM (this is in contrast to WGM for Woman Grandmaster and IM for International Master).
Normally three favorable results (or norms) in tournaments involving other Grandmasters are required before FIDE will confer the title on a player. There are other milestones a player can achieve to get the title, such as qualifying for the Candidates tournament. The Candidates Tournaments, now defunct, were a series of tournaments whose winner earned the right to challenge the reigning world champion. Bobby Fischer got his Grandmaster title by qualifying for the 1959 Candidates Tournament, at the ripe old age of 15. In 2002, twelve year old Ukrainian Sergey Karjakin became the youngest Grandmaster ever.
Grandmasters normally have an Elo chess rating of over 2500. Players from 2400-2500 normally have acquired the International Master (IM) title.
The title "Grandmaster" was created by Russian Tsar Nicholas II who first awarded it in 1914 to five players (Lasker, Capablanca, Alekhine, Tarrasch and Marshall) after a tournament in Saint Petersburg which he had funded.
See list of chess players for more.