John Nicholas Sandlin (born February 24, 1872) was a Democratic member of the United States House of Representatives from Louisiana. He represented Louisiana’s 4th Congressional District and served as a federal legislator during the early to mid-twentieth century. Sandlin’s tenure in Congress began on April 11, 1921, and continued until January 3, 1937, spanning eight consecutive terms in the House.

As a Representative from Louisiana, Sandlin served in the U.S. Congress for sixteen years, participating in national legislative affairs during a period marked by significant political and economic change. He was affiliated with the Democratic Party throughout his service. After leaving office in 1937, he was regarded as a historical member of Congress, having played a sustained role in representing the interests of Louisiana’s 4th District at the federal level.