The Davis Cup is the premier international team event in men's tennis. It is organised by the International Tennis Federation (ITF) and contested annually between teams from over 150 competing countries, making it the world's largest annual team sporting competition. It is described by the organisers as the "World Cup of Tennis" and the winners are referred to as the world champions. The competition began in 1900 as a challenge between Great Britain and the United States. By 2023 155 nations entered teams into the competition.