The fourth season of the American television series Bones premiered on September 3, 2008, with a two-hour episode and concluded on May 14, 2009, on Fox. The show changed time slots again, airing on Wednesdays at 8:00 pm ET before moving to Thursdays at 8:00 pm ET in 2009. The season consisted of 26 episodes and averaged 10.8 million viewers.

Dr. Temperance "Bones" Brennan, Ph.D. is a fictional character portrayed by Emily Deschanel in the American Fox television series Bones. An anthropologist, forensic anthropologist, and kinesiologist, she is described in the series as a leading authority in the field of forensic anthropology. Brennan first appeared on television, along with other series characters, in the "Pilot" episode of Bones on September 13, 2005. She is the main protagonist of the series along with FBI Special Agent Seeley Booth.