Middleton is a city in Canyon County, Idaho, United States. The population was 5,524 at the 2010 census, up from 2,978 in 2000. It is part of the Boise City–Nampa, Idaho Metropolitan Statistical Area.
Middleton was named for its location between the old fort Boise and Keeney's Ferry; it being the midpoint between the two. It served as a rest stop for those heading for Keeney's Ferry. It had a stage station in the early days of the Oregon Trail, a post office in 1866 and a water powered grist mill in 1871. The Ward Massacre occurred near the site in 1854.
Middleton is the oldest settlement in Canyon County, with the land being parceled out in 1863 by William N. Montgomery. The Boise River flooded in 1872 and cut a new channel, isolating the town on an island; as a result, the town moved to a new location in the years after 1880. The town incorporated as a city in 1910, although the certificate was not issued until 1971. The present mayor is Steve Rule.
On February 1, 2007, 78% of Middleton High School burned down, caused by the overheating of a fan above the weight room.