Para-swimming classification is a function-based classification system designed to allow for fair competition in disability swimming. The classes are prefixed with "S" for freestyle, butterfly and backstroke events, "SB" for breaststroke and "SM" for individual medley events. Swimmers with physical disabilities are divided into ten classes based on their degree of functional disability: S1, S2, S3, S4, S5, S6, S7, S8, S9 and S10. The lower number indicates a greater degree of impairment. Those with visual impairments are placed in three additional classes: S11, S12 and S13. One more class, S14, is reserved for swimmers with intellectual impairment. A final class, S15, is for athletes with hearing loss. Another Classification is S19 which is similar to S14. It differs because S14 swimmers have an Iq of below 75 whereas S19 swimmers have an Iq of above 75.
Swimming was one of the first organised sports for people with disabilities, and was contested at the first Summer Paralympics in 1960. Both the rules for the sport and approval of classifications were the responsibility of the Fédération International de Natation Amateur (FINA) until 1992, when the International Paralympic Committee took over the governance of classification. As of 2012, people with visual, physical and intellectual disabilities are eligible to compete in the sport. The classification system was originally based on medical criteria, but has since moved to one largely based on functional disability to make para-swimming more competitive. The sport is moving towards an evidence-based classification system.