Spencer is a city in Clark County, Idaho, United States. The population was 38 at the 2000 census.
The city is noted as being the "Opal Capital of America". The mine is located 5–6 miles outside of town.
Spencer is located at 44°22′2″N 112°11′32″W / 44.36722°N 112.19222°W / 44.36722; -112.19222 (44.367316, -112.192170).