Lucien Marion Gex (September 24, 1907 - October 6, 1971) was an American lawyer and politician. He was a member of the Mississippi House of Representatives, representing Hancock County, from 1936 to 1940.

Lucien Marion Gex was born on September 24, 1907, in Bay St. Louis, Hancock County, Mississippi.^[1][2][3] He was the son of Walter J. Gex and Amanda (VanGohren) Gex.^[3] Lucien graduated from St. Stanislaus High School in Bay St. Louis, and from the Tulane School of Law in New Orleans.^[3] He began practicing law in 1930.^[3] He then served as the City Attorney of Bay St. Louis.^[1][3] Gex was elected to represent Hancock County in the Mississippi House of Representatives from 1936 to 1940.^[1] In the House, he was a member of the Banks and Banking; Fisheries, Commerce, and Shipping; Municipalities; and Judiciary "A" committees.^[1] Gex also served as the first president of the Hancock County Bar Association.^[3] Gex died of a heart attack on October 6, 1971, at Hancock General Hospital in Bay St. Louis.^[2][3]

Gex was a Roman Catholic.^[1][3] He was married to Geraldine and had 3 children and 12 grandchildren.^[3] Lucien Gex's relatives Emile J. Gex and Walter Phillips also both served in the Mississippi Legislature.^[4]