Timothy Ross Armstrong is an American musician, songwriter and record producer. Known for his distinctive voice, he is the singer/guitarist for the punk rock band Rancid and hip hop/punk rock supergroup Transplants. Prior to forming Rancid, Armstrong was in the ska punk band Operation Ivy.

Rancid is an American punk rock band formed in Berkeley, California in 1991. Founded by Tim Armstrong and Matt Freeman, former members of the band Operation Ivy, Rancid is often credited as being among the wave of bands that revived mainstream interest in punk rock in the United States during the mid-1990s. Over its 33-year career, Rancid has retained much of its original fan-base, most of which was connected to its underground musical roots.