Current season, competition or edition: 2023–24 A1 Ethniki | |
 | |
| Sport | Water polo |
|---|---|
| Founded | 1927 |
| Administrator | Hellenic Swimming Federation |
| No. of teams | 16 |
| Country | Greece |
| Confederation | LEN |
| Most recent champion(s) | Olympiacos Piraeus (2023–24) |
| Most titles | Ethnikos Piraeus Olympiacos Piraeus (38 titles) |
| TV partner(s) | ERT |
| Level on pyramid | Level 1 |
| Relegation to | A2 Ethniki Water Polo |
| Domestic cup(s) | Greek Cup |
| International cup(s) | LEN Champions League LEN Euro Cup |
| Official website | koe.org.gr |
The A1 Ethniki (Greek: Α1 Εθνική Κατηγορία), often referred to as the Greek Water Polo League, is the highest professional water polo league in Greece. It is run by the Hellenic Swimming Federation. It is considered one of the top national leagues in European water polo, as its clubs have made significant success in European competitions.
Ethnikos Piraeus and Olympiacos Piraeus share the most championships, having 38. Ethnikos also has the record for consecutive championships, with 18.