Carbon is a city in Douglas Township, Adams County, Iowa, United States. The population was 34 at the 2010 census.
Note that other places in Iowa have been named Carbon. There was a Carbon Post Office in Davis County, 6 miles south of Ottumwa, that operated for less than a year in 1881. There was also a Carbon Post Office in Webster County, 3 miles south-east of Fort Dodge, that operated from 1870 to 1872. A post office on the latter location was known as Gypsum from 1902 to 1905.