Ângelo César do Rosário Firmino, better known by the stage name Boss AC (born January 20, 1975) is a Portuguese rapper originally from Cape Verde.

Boss AC started his career in 1994 with Rapública, a compilation album that joined together the new faces of the Portuguese hip hop movement.

The album earned Boss AC a nomination in the MTV Europe Music Awards for Best Portuguese Act.

[1] His fifth fourth album Preto no Branco (Black on White) was released in January 2008 and features the single "Levanta-te" (Stand-up), its music video was launched on the Portuguese MTV later on 21 July.

His fifth album AC Para os Amigos (Nickname AC) was edited on 6 February 2012 and would be released by Universal Music, singles included in the album are "Sexta-feira (Emprego Bom Já)", "Tástabater" and "Tu Es Mais Forte".