Medley is a combination of four different swimming styles — butterfly stroke, backstroke, breaststroke, and freestyle — into one race. This race is either swum by one swimmer as individual medley (IM) or by four swimmers as a medley relay. In medley swimming, each swimmer uses a different stroke (in this order): backstroke, breaststroke, butterfly, and freestyle, with the added limitation that the freestyle swimmer cannot use any of the first three strokes. At competitive levels, essentially all freestyle swimmers use the front crawl. The three standard relays raced at the Olympics are the 4 × 100 m freestyle relay, 4 × 200 m freestyle relay and 4 × 100 m medley relay. Mixed-gendered relays were introduced at the 2014 FINA World Swimming Championships (25 m) (4 × 50 m freestyle and medley) and the 2015 World Aquatics Championships (4 × 100 m freestyle and medley). The event will debut at the 2020 Summer Olympics (4 × 100 m medley).
Individual medley: Individual medley consists of a single swimmer swimming equal distances of four different strokes within one race.
Stroke order: Individual medley consists of four strokes. The swimmer will swim one quarter of the race in each style, in a certain order. The strokes are swum in this order:
- Freestyle (this can be any stroke except the butterfly, backstroke, or breaststroke; most swimmers use the front crawl)
Competitions: A number of competitions in the individual medley are regularly contested, by both men and women. The competitions are limited in that every distance must consist of either four lengths of the pool (100 yard or meter) or a multiple of four lengths (200 or 400 yard or meter), so that no stroke must change mid-length.
- 100 m/yd individual medley: Swum in short course (25 m/yd pool) competition only. This is not an Olympic event.
- 200 m/yd individual medley: Swum in both short course and long course (50 m pool) competitions. This was swum as an Olympic event in the 1968 Summer Olympics, Mexico City, Mexico but then omitted until the 1984 Summer Olympics, Los Angeles, United States. The event has been swum ever since.
- 400 m/yd individual medley: Swum in both short course and long course competitions. This has been an Olympic event since the 1964 Summer Olympics, Tokyo, Japan.
Medley relay: Medley relay consists of four different swimmers in one relay race, each swimming one of the four strokes.
Stroke order: Medley relay is swum by four different swimmers, each swimming one of the four strokes. Backstroke is the first event as backstroke is started from the water. If backstroke were not the first event, the starting backstroke swimmer and the finishing previous swimmer could block each other. The remaining strokes are sorted according to the speed, with breaststroke being the slowest and freestyle being the fastest stroke. The order of the strokes is as follows:
- Freestyle the only limitation being that none of backstroke, breaststroke, or butterfly stroke may be used for this leg. Most swimmers use the front crawl.
Competitions: There are a number of competitions swum regularly in medley relay, both by men and women.
- 4×50 m/yd medley relay: Swum in both short course and long course pools. This is not an Olympic competition.
- 4×100 m/yd medley relay: Swum in both short course and long course pools. This was the first Olympic medley competition and is swum since the 1960 Summer Olympics, Rome, Italy. The first Olympic butterfly event itself was first swum in the previous 1956 Summer Olympics.
Rules: These are the official rules of the FINA regarding medley swimming:
- In relay events, the team of a swimmer whose feet lose touch with the starting platform before the preceding team-mate touches the wall shall be disqualified, unless the swimmer in default returns to the original starting point at the wall, but it shall not be necessary to return to the starting platform.
- Any relay team shall be disqualified from a race if a team member, other than the swimmer designated to swim that length, enters the water when the race is being conducted, before all swimmers of all teams have finished the race.
- The members of a relay team and their order of competing must be nominated before the race. Any relay team member may compete in a race only once. The composition of a relay team may be changed between the heats and finals of an event, provided that it is made up from the list of swimmers properly entered by a member for that event. Failure to swim in the order listed will result in disqualification. Substitutions may be made only in the case of a documented medical emergency.
- Any swimmer having finished his race, or their distance in a relay event, must leave the pool as soon as possible without obstructing any other swimmer who has not yet finished their race. Otherwise the swimmer committing the fault, or their relay team, shall be disqualified.
- There shall be four swimmers on each relay team.