| Nextseason: | 2021–22 |
| Season: | 2020–21 |
| E.ON Férfi OB I Bajnokság1 | |
| Extra Information: | 1 Sponsored league name, referring to E.ON. |
| T Bg: |
|
| Teams: | 16 |
| Duration: | – (Regular season) |
| Tv: | M4 Sport |
| Mvp Link: | BLS First League MVP |
| Finals Mvp Link: | BLS Playoff MVP |
| Top Scorer: | Mátyás Pásztor(90 goals) |
| Winning Streak: | 16 games Szolnok |
| Losing Streak: | 14 games Tatabánya |
| Biggest Home Win: | (4 November 2020) |
| Biggest Away Win: | (27 October 2020) |
The 2020–21 Országos Bajnokság I (also known as the E.ON Férfi OB I Bajnokság for sponsorship reasons, OB I in short), is going to be the 115th season of top-tier water polo in Hungary.
The following 16 clubs compete in the OB I during the 2020–21 season:
| Team | Home city | Pool | Colours | |
|---|---|---|---|---|
| BVSC | Budapest (XIV. ker) | Szőnyi úti Uszoda | ||
| Debrecen | Debrecen | Debreceni Sportuszoda | ||
| Eger | Eger | Bitskey Aladár Uszoda | ||
| FTC | Budapest (IX. ker) | FTC uszoda, Népliget | ||
| Honvéd | Budapest (XIX. ker) | Kőér utcai Uszoda | ||
| Kaposvár | Kaposvár | Csík Ferenc Sportuszoda | ||
| KSI | Budapest | Széchy Tamás Uszoda | ||
| Miskolc | Miskolc | Kemény Dénes Sportuszoda | ||
| OSC | Budapest (XI. ker) | Nyéki Imre Uszoda | ||
| PVSK | Pécs | Abay Nemes Oszkár Sportuszoda | ||
| Szeged | Szeged | Tiszavirág Sportuszoda | ||
| Szentes | Szentes | Dr. Rébeli Szabó József Sportuszoda | ||
| Szolnok | Szolnok | Tiszaligeti Uszoda | ||
| Tatabánya | Tatabánya | Tatabányai Sportuszoda | ||
| UVSE | Budapest (IV. ker) | Komjádi Béla Sportuszoda | ||
| Vasas | Budapest (XIII. ker) | Komjádi Béla Sportuszoda |
| Team | Head coach | Captain | Cap manufacturer | Cap sponsors | |
|---|---|---|---|---|---|
| BVSC |  Kristóf Kemény | Mátyás Pásztor | Diapolo | MKB-Euroleasing | |
| Debrecen |  Miroslav Bajin | Máté Süveges | Diapolo | none | |
| Eger | Márton Petrovai | Máté Sántavy | Diapolo | Tigra, ZF | |
| FTC | Zsolt Varga | Dénes Varga | Diapolo | Telekom, MVM | |
| Honvéd | Márton Szívós | Arena | none | ||
| Kaposvár | László Surányi | Ferenc Vindisch | Seles | none | |
| KSI | Dániel Horváth | Diapolo | none | ||
| Miskolc | István Kis |  Lukáš Seman | Diapolo | PannErgy | |
| OSC | Dániel Varga | Balázs Erdélyi | Diapolo | MOL | |
| PVSK | Viktor Török | Diapolo | none | ||
| Szeged | Zoltán Szabó | Csaba Kiss | Diapolo | none | |
| Szentes | Csaba Pellei | Balázs Somogyi | Yordo | metALCOM | |
| Szolnok | Živko Gocić | Dániel Angyal | Arena | none | |
| Tatabánya | Tamás Zantleitner | Márton Keresztúri | Arena | none | |
| UVSE | Balázs Vincze | Balázs Korényi | Diapolo | none | |
| Vasas | Lajos Vad | Bence Bátori | Diapolo | A-Híd, Plaket |
In the table below the home teams are listed on the left and the away teams along the top.
| Team 1 | Points | Team 2 | Regular season | Game 1 | Game 2 | Game 3 | ||
|---|---|---|---|---|---|---|---|---|
| Szolnoki Dózsa (1) | 7–1 | 13−12 | 8−8 | 11−7 | ／ | |||
| OSC Újbuda (2) | 6–3 | 9−7 | 16−12 | 2-7 | − |
Szolnoki Dózsa won the series 7–1 with points ratio, and advanced to the Finals.------