Green Clay Smith (July 4, 1826 – June 29, 1895) was a United States soldier and politician.

Elected to the Kentucky state house before the American Civil War, he was commissioned as a Union officer when he volunteered, advancing to the rank of brigadier general before he resigned to go to Congress.

He was named for his maternal grandfather, Green Clay, a very wealthy planter and slaveholder in Kentucky and a prominent politician.

His siblings included Sally Ann Lewis (1818–1875),[1] named for her maternal grandmother; Curran Cassius, Pauline Green, Junius Brutus (never married), Mary Spencer (never married), and John Speed Jr.[2] Smith's father was elected to the Kentucky legislature and the U.S. House of Representatives.

When the U.S.-Mexican War began, he enlisted in the Army and was commissioned as a second lieutenant in the First Regiment of the Kentucky Volunteer Infantry on June 9, 1846.

Smith returned to Kentucky, where he graduated from Transylvania University in 1849, then studied law and was admitted to the bar in 1852.

Smith resigned from Congress in July 1866 when President Andrew Johnson appointed him as Territorial Governor of Montana.