The 1999–2000 Nemzeti Bajnokság I, also known as NB I, was the 98th season of top-tier football in Hungary.
The league was officially named Professzionális Nemzeti Bajnokság (PNB) for sponsorship reasons.
It was contested by 18 teams, and Dunaferr FC won the championship under coach Sándor Egervári.
Dunaferr finished an astounding 15 points above runners-up and defending champions MTK and lost only one game throughout the entire campaign.
Note: Gázszer FC completed the autumn season, Pecs played in the spring.