Campeonato Nacional de Juniores B/Juvenis is the top level of the Portuguese football league system for youth players 17-year-old and under.

The league started in 1962 and has been historically dominated by the Big Three clubs.

The Campeonato Nacional de Juvenis begins in mid-August and ends in June.

The Nacional de Juvenis season is played in three phases.

The third phase is a single group of six teams that face each other to determine the champion.