Ten nations competed in water polo at the 1956 Summer Olympics in Melbourne. The event was open only to men's teams.
For the team rosters see: Water polo at the 1956 Summer Olympics - Men's team squads.
The preliminary round consisted of a round-robin tournament held in three groups. Each team played the other teams in its group once.
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The top two teams in each preliminary group advanced to the championship, in which they played each of the four other championship teams they had not previously faced. The results of the preliminary round game against the team from their group carried over into the final round.
The teams that did not advance to the championship played in a consolation tournament.
The most famous water polo match in history is the semi-finals round match between Hungary and the Soviet Union. As the athletes left for the games, the Hungarian Revolution started and was crushed by the Soviet army. Many of the Hungarian athletes vowed never to return home and felt their only means of fighting back was in the pool.
With only two games left for each team, the Hungarians were leading in the standings, 1 point ahead of Yugoslavia and 2 ahead of the Soviets. A Soviet victory would have put them alongside the Hungarians in the standings, with the final match pairings favoring the Soviets, who would face the last-place Germans while Hungary had to compete with Yugoslavia. A Hungarian victory would ensure at least a silver medal for the team, with a draw or a win against Yugoslavia in the last game meaning gold.
The Hungary-Soviet Union confrontation was extremely bloody and violent, riddled with penalties, and the pool was later depicted as turning red from the blood spilt. The Hungarians led the Soviets 4-0 before the game was called off in the final minute to prevent angry spectators, many of them Hungarian immigrants to Australia, reacting to Valentin Prokopov punching Ervin Zador's eye open. The Hungarians went on to win the gold medal by defeating Yugoslavia 2-1 in the final. Half of the Hungarian Olympic delegation defected after the Games.