Országos Bajnokság I (English: Nationwide Championship I, commonly abbreviated OB I) is the highest level water polo league for men in Hungary, that is administered and supervised by the Hungarian Water Polo Federation.

[1] The following 14 clubs compete in the OB I during the 2022–23 season: The number of seasons that each team (in alphabetical order) has played in the top division from 1904 until 2021–22.

A total of 61 teams had competed in at least one season at the top division.

Ferencváros is the only teams to have played in the top division in every season since the league's inception in its modern form.

As we can see from the chart the number of teams in the Hungarian First Division changed a lot and continuously.