The Triple Nine Society (TNS), founded in 1978, is a voluntary association of individuals who have scored at or above the 99.9th percentile on specific IQ tests (or similar) under supervised conditions, which (leaving aside the issue of error of measurement in the tests) generally corresponds to an IQ of 149 or greater using a standard deviation of 16 (e.g. Stanford-Binet IV) and 146 or greater with a standard deviation of 15 (e.g. Stanford-Binet 5). This compares with Mensa International, the better-known and larger membership high IQ society which admits applicants who score at or above the 98th percentile, which generally corresponds with an IQ score of 131 (SD 15) or 133 (SD 16), or greater.
TNS publishes a journal entitled Vidya which contains articles contributed by members conversant with a variety of subjects. Members communicate with one another through email lists, a Facebook group, two Yahoo! Groups, a Linked-In group and a scheduled weekly IRC chat, and meet at arranged gatherings; European members have established a group in XING. TNS also sponsors annual meetings in the US ("ggg999") and in Europe ("egg999").
The Triple Nine Society was founded on democratic principles. TNS states that the group encourages the free expression of member views.