The Davis Cup is the premier international team event in men's tennis. It is run by the International Tennis Federation (ITF) and is contested annually between teams from competing countries in a knock-out format. It is described by the organisers as the "World Cup of Tennis", and the winners are referred to as the World Champion team. The competition began in 1900 as a challenge between Great Britain and the United States. By 2016, 130 nations entered teams into the competition. The most successful countries over the history of the tournament are the United States (winning 32 tournaments and finishing as runners-up 29 times) and Australia (winning 28 times, including four occasions with New Zealand as Australasia, and finishing as runners-up 19 times). The present champions are Great Britain who beat Belgium to win the title for the 10th time in 2015. It was Great Britain's first title in 79 years, and first in the open era. The win moved Great Britain to third on the all time winners list.