Def Con Dos (meaning DEFense CONdition TWO) is a rap rock band from Madrid, Spain.

Greatly influenced by hip hop bands Beastie Boys, Public Enemy, and Run D.M.C., and rock band Siniestro Total, they started rapping over hip hop bases created by producer Julián Hernández (musician and singer of Siniestro Total). In their Segundo Asalto tape (1989), the sound still was basically hip hop, but they started using rock guitars.