Burley is a city in Cassia and Minidoka counties in the southern portion of the U.S. state of Idaho. The population was 10,345 at the 2010 census. The city is the county seat of Cassia County. Burley is the second-largest city in Idaho's Magic Valley region after Twin Falls. Along with nearby Rupert it forms the bulk of the "Mini-Cassia" area of southern Idaho. Burley is the principal city of the Burley, ID Micropolitan Statistical Area, which includes Cassia and Minidoka Counties. Burley is home to the famed "Spudman" Triathlon.