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 considered one of the top national leagues in European water polo, as its clubs have made significant success in European competitions.

Ethnikos also has the record for consecutive championships, with 18.

The Hellenic Swimming Federation declares all championship winning teams as champions from 1928 and onwards.

Teams in bold participate in the 2023–24 season.