DYS was a straight edge hardcore punk band from Boston, Massachusetts, and part of the notorious Boston Crew along with contemporaries such as SSD and Negative FX. They released two LPs: Brotherhood, an album still held in high regard by fans of hardcore music, and DYS (i.e., self-titled), an album that is more a hard rock or heavy metal album than a hardcore album. Both albums have been reissued together on a CD by Taang! Records (titled Fire and Ice), and Brotherhood has been reissued on vinyl by Reflex Records (as Wolfpack, with additional tracks).

DYS took its name from the Department of Youth Services, a Boston governmental organization infamous for mistreatment of its charges (cases of physical brutality, rape, and professional misconduct are well-documented). Singer Dave Smalley went on to sing for Dag Nasty, ALL and Down By Law. Bassist Jonathan Anastas became founding member of Slapshot.