Idaho Legislative District 21 is one of 35 districts of the Idaho Legislature. It is currently represented by Clifford Bayer, Republican of Meridian,Steven Harris, Republican of Meridian, and Thomas Dayley, Republican of Boise.
From 1984 to 1992, District 21 was a floterial district that contained Districts 14, 15, 16, 17, 18, 19, and 20. District 21 consisted of all of Ada County.
From 1992 to 2002, District 21 consisted of Blaine, Camas, Lincoln Counties a portion of Elmore and Gooding Counties.
From 2002 to 2012, District 21 consisted of a portion of Ada County.
District 21 currently consists of a portion of Ada County.