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. If 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.

Greece
 Greece's final squad was announced on 3 July 2021.

Head coach: Thodoris Vlachos

Note: Age as of 23 July 2021 Source: Greece Men | Tokyo 2020 Olympics 

Hungary
 Hungary's final squad was announced on 29 June 2021.

Head coach: Tamás Märcz

Note: Age as of 23 July 2021 Source: Hungary Men | Tokyo 2020 Olympics 

Italy
 Italy's final squad was announced on 2 July 2021.

Head coach: Sandro Campagna

Note: Age as of 23 July 2021 Source: Italy Men | Tokyo 2020 Olympics 

Japan
 Japan's final squad was announced on 19 May 2021.

Head coach: Yoji Omoto

Note: Age as of 23 July 2021 Source: Japan Men | Tokyo 2020 Olympics 

South Africa
<section begin=RSA /> South Africa's squad was announced on 24 June 2021. Roarke Olver was replaced by Timothy Rezelman.

<section begin=RSAWPT />Head coach: Paul Martin

Note: Age as of 23 July 2021 Source: South Africa Men | Tokyo 2020 Olympics <section end=RSAWPT /><section end=RSA />

United States
<section begin=USA /> The United States' final squad was announced on 2 July 2021.

<section begin=USAWPT />Head coach: 🇷🇸 Dejan Udovičić

Note: Age as of 23 July 2021 Source: United States Men | Tokyo 2020 Olympics <section end=USAWPT /><section end=USA />

Australia
<section begin=AUS /> Australia's final squad was announced on 1 July 2021.

<section begin=AUSWPT />Head coach: Elvis Fatović

Note: Age as of 23 July 2021 Source: Australia Men | Tokyo 2020 Olympics <section end=AUSWPT /><section end=AUS />

Croatia
<section begin=CRO /> Croatia's final squad was announced on 8 July 2021.

<section begin=CROWPT />Head coach: Ivica Tucak

Note: Age as of 23 July 2021 Source: Croatia Men | Tokyo 2020 Olympics <section end=CROWPT /><section end=CRO />

Kazakhstan
<section begin=KAZ /> <section begin=KAZWPT />Head coach: 🇲🇪 Nemanja Knežević

Note: Age as of 23 July 2021 Source: Kazakhstan Men | Tokyo 2020 Olympics <section end=KAZWPT /><section end=KAZ />

Montenegro
<section begin=MNE /> Montenegro's final squad was announced on 8 July 2021.

<section begin=MNEWPT />Head coach: Vladimir Gojković

Note: Age as of 23 July 2021 Source: Montenegro Men | Tokyo 2020 Olympics <section end=MNEWPT /><section end=MNE />

Serbia
<section begin=SRB /> Serbia's final squad was announced on 8 July 2021.

<section begin=SRBWPT />Head coach: Dejan Savić

Note: Age as of 23 July 2021 Source: Serbia Men | Tokyo 2020 Olympics <section end=SRBWPT /><section end=SRB />

Spain
<section begin=ESP /> Spain's final squad was announced on 9 July 2021.

<section begin=ESPWPT />Head coach: David Martín

Note: Age as of 23 July 2021 Source: Spain Men | Tokyo 2020 Olympics <section end=ESPWPT /><section end=ESP />