The Grandmaster title is awarded by FIDE and the requirements as follows:
1. A player must have an ELO of at least 2500 at some time or other.
2. Two winning results (norms) must be attained in tournaments involving other Grandmasters, including Grandmaster’s from countries other than than the applicant’s.
3. The minimum rating of the opponents must be greater than 2250.
4. The applicant must play at least 9 games in each of the tournaments to qualify and needs a total of 27 games in 2 or more norms.
5. Title results remain valid for life.
More details can be found on the online FIDE handbook.