The 1998–99 season of Segunda División B of Spanish football started in August 1998 and ended in May 1999 after the play-offs.
Playoffs de Ascenso: Relegated from Segunda División: Promoted from Tercera División: Relegated: Teams from Asturias, Canary Islands, Castilla–La Mancha, Community of Madrid and Galicia
Teams from Aragon, Basque Country, Cantabria, Castile and León, Castilla–La Mancha, La Rioja and Navarre.
Teams from Catalonia, Region of Murcia and Valencian Community.
Teams from Andalusia, Castilla–La Mancha, Ceuta, Extremadura and Melilla.