Radiosport (or radio sport) is formal competition between amateur radio operators in any of three amateur radio activities.
The Friendship Radiosport Games is an international multi-sport event that includes all three types of radiosport. Since 1977, the International Amateur Radio Union has sponsored the IARU HF World Championship (originally named the IARU Radiosport Championship). The World Radiosport Team Championship is another international competition, is considered by many to be the closest that contesting has to a world championships -- similar to the World Series, Super Bowl, or World Cup.

The most common use of the term radiosport is as a synonym for amateur radio contesting (ham radio contesting). Contesting is an activity where amateur radio stations attempt to make as many two-way contacts with other stations as possible, following certain defined parameters of the competition, to maximize a score.

In the US, the major contests are sponsored by ARRL, CQ Amateur Radio, and the National Contest Journal (NCJ). There are also many other contest sponsors from around the world. And each of the 50 US States conducts their own "State QSO Party" each year. See the chart below.