Lewis Cass Ledyard (April 4, 1851 – January 27, 1932) was a New York City lawyer, a name partner at the firm Carter Ledyard & Milburn, personal counsel to J.P. Morgan, and a president of the New York City Bar Association.
Lewis Cass Ledyard was born in Detroit, Michigan, in 1851, to an established American family. His grandfather, General Lewis Cass, had been governor of the Michigan Territory and a United States senator from the state of Michigan, and served as secretary of state under President James Buchanan. His ancestors included Major-General Joseph Spencer, who served in the American Revolution under George Washington, and William Livingston, the first governor of New Jersey.
His father, Henry Ledyard, was a lawyer, diplomat, and mayor of Detroit. His mother, Matilda Frances, was the daughter of General Cass. Lewis Cass Ledyard was the fourth child in a family of three daughters and two sons. His older brother, Henry Brockholst Ledyard, later became president of the Michigan Central Railroad and a well-known philanthropist.