Walter Guion (April 3, 1849 – February 7, 1927) was a United States senator from Louisiana.

Born near Thibodaux, he was tutored at home and then attended Jefferson College in St. James Parish.

Guion was appointed by President Woodrow Wilson to the office of United States Attorney for the eastern district of Louisiana, which he held from 1913 to 1917, when he resigned.

On April 22, 1918, Guion was appointed as a Democrat to the U.S. Senate to fill the vacancy caused by the death of Robert F. Broussard and served from April 22, 1918, until November 5, 1918, when a successor was elected; while in the Senate he was chairman of the Committee on Coast and Insular Survey (Sixty-fifth Congress).

He practiced law in New Orleans until his death in that city on in 1927; interment was in Metairie Cemetery.