Water polo at the 2020 Summer Olympics – Men's team rosters
These are the rosters of all participating teams at the men's water polo tournament at the 2020 Summer Olympics in Tokyo. The twelve national teams were required to submit squads of 12 players. Additionally, teams could name one alternate player. In the event that a player on the submitted squad list suffered an injury or illness, that player would be able to be replaced by the player in the alternate list. On 3 July 2021, the International Olympic Committee (IOC) confirmed that there was a change for the  2020 Summer Olympics, allowing all 13 water polo players named to be available on the roster, with 12 being named for each match. This change was implemented due to the challenges of the COVID-19 pandemic. As of 2 August 2021, all players competed in the men's tournament. Group A. Greece. The Greece's final squad was announced on 3 July 2021. Head coach: Thodoris Vlachos Hungary. The Hungary's final squad was announced on 29 June 2021. Head coach: Tamás Märcz Italy. The Italy's final squad was announced on 2 July 2021. Head coach: Sandro Campagna Japan. The  Japan's final squad was announced on 19 May 2021. Head coach: Yoji Omoto South Africa. The South Africa's squad was announced on 24 June 2021. Roarke Olver was replaced by Timothy Rezelman. Head coach: Paul Martin United States. The United States' final squad was announced on 2 July 2021. Head coach: Dejan Udovičić Group B. Australia. The Australia's final squad was announced on 1 July 2021. Head coach: Elvis Fatović Croatia. The Croatia's final squad was announced on 8 July 2021. Head coach: Ivica Tucak Kazakhstan. Head coach: Nemanja Knežević Montenegro. The Montenegro's final squad  was announced on 8 July 2021. Head coach: Vladimir Gojković Serbia. The Serbia's final squad was announced on 8 July 2021. Head coach: Dejan Savić Spain. The Spain's final squad was announced on 9 July 2021. Head coach: David Martín