IAAF World Cross Country Championships is the most important competition in international Cross country running. Held annually and organised by International Association of Athletics Federations, it was inaugurated in 1973, when it replaced the International Cross Country Championships.

Traditionally, the World Cross Country Championships consisted of four races: one each for men (12km) and for women (8km); and one each for junior men (8km) and for junior women (6km). Scoring was done for individuals and for national teams. In the team competition, the finishing positions of the top six scorers from a team of up to nine are summed for the men and women, respectively, and the low score wins. For the junior races, the top three from a team of up to four are scored.

The year 1998 saw the introduction of two new events at the World Cross Country Championships, a short race for men and a short race for women. The last time these 4km races were held was 2006, and there are no public plans to bring them back.

Many consider the World Cross Country Championships to be the most difficult races to win, even more difficult than the Olympic Games. At most major championships, the world's best distance runners are separated into a few races, i.e. 3000m Steeplechase, 5000m, and 10,000m. However, in the absence of the short course races, the World Cross Country Championships pit all runners against one another in only one race. Thus, the competition is quite fierce. It's no wonder, then, that several Olympic Champions have gotten their start as World Cross Country Champions: Carlos Lopes, marathon, 1984; John Ngugi, 5000m, 1988; Khalid Skah, 10,000m, 1992; and Kenenisa Bekele, 10,000m, 2004. Numerous other champions have medalled at the Olympic Games or the World Championships, or have set World Records.