Országos Bajnokság I (men's water polo)
Országos Bajnokság 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. Since 2009, after signed a four-year sponsorship contract with telecommunications company Vodafone, the competition is officially known as Vodafone OB I. Current teams. The following 14 clubs compete in the OB I during the 2021–22 season: Most seasons. 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. The teams in Bold participate in the 2021–22 OB I. Format. As we can see from the chart the number of teams in the Hungarian First Division changed a lot and continuously. The league started in 1904 with four teams and with the formation of teams the league expanded continuously. Currently, there are 14 teams in the first division. Országos Bajnokság I (men's water