Josiah Stoddard Johnston (November 24, 1784 – May 19, 1833) was an American politician who served as both United States representative and Senator for Louisiana.

He graduated from Transylvania University (Lexington, Kentucky) in 1802, studied law, was admitted to the bar, and commenced practice in Alexandria, Louisiana (then the Territory of Orleans).

He was a member of the Territorial legislature from 1805 to 1812 and during the War of 1812 raised and organized a regiment for the defense of New Orleans, but reached the city after the battle.

While in the Senate he was chairman of the Committee on Commerce (Nineteenth Congress); interment was in Rapides Cemetery, Pineville, Louisiana.

[1] His son, J. Stoddard Johnston (1833–1913), a journalist and editor, also served during the War, eventually becoming Kentucky's Secretary of State.