Lloyd Carpenter Griscom (November 4, 1872 – February 8, 1959) was an American lawyer, diplomat, and newspaper publisher.

Lloyd Griscom was born on November 4, 1872, at Riverton, New Jersey. He was the son of shipping magnate Clement Griscom (1841–1912) and Frances Canby Biddle (1840–1923). Among his siblings was Frances Griscom, an amateur golfer who won the 1900 U.S. Women's Amateur held at Shinnecock Hills Golf Club in Southampton, New York, She and played in the 1898 Amateur at the Ardsley Club.

He graduated in 1891 from the law department of University of Pennsylvania and a member of the Sigma chapter of the Zeta Psi Fraternity. Griscom continued his legal studies at the New York Law School. He later received a Doctor of Laws from the University of Pennsylvania in 1907.

In 1893–1894, Griscom served in the United Kingdom as secretary to Ambassador Thomas Bayard; he was admitted to the bar in 1896, and the following year in 1897 he was deputy district attorney of New York. During the Spanish–American War, he served as captain and assistant quartermaster.

While serving a short period as Secretary of Legation and chargé d' affaires at Constantinople, the 28-year-old Griscom made a notable achievement in 1900 by persuading the Sultan to purchase what would become the Ottoman cruiser Mecidiye from the American shipbuilder William Cramp & Sons. Shortly afterward, he was appointed Minister to Persia in 1901. He held the corresponding post in Japan (1902–1906) and was ambassador to Brazil (1906–1907) and to Italy (1907–1909).

In 1911, he became a member of the law firm of Beekman, Menken, and Griscom, New York City, and was thereafter active in local Republican politics, helping found The New York Young Republican Club. He contributed numerous articles to the Philadelphia Sunday Press on travel in Central America. In 1917, he was appointed a major in the department of the Adjutant-General of the United States Army and afterward became Assistant Adjutant-General. During the war, he served as liaison officer to General John J. Pershing, commander of the American Expeditionary Forces of the U.S. Army. He was a close friend of Col. Theodore Roosevelt Jr.

Griscom's primary significance was as an advocate for globalized free trade as a means to promote peaceful development in accordance with his Quaker faith. In the Middle East he worked for better relations between Muslims and Christians, and he played a major role in the relief effort in Italy after the 1908 Messina earthquake took 50,000 lives. Prior to the death of Secretary of State John Hay in 1905, Griscom was offered the post of First Assistant Secretary of State. The appointment of Elihu Root to succeed Hay nullified Griscom's appointment to the State Department position.

In 1940, he published a memoir of his professional life, Diplomatically Speaking, covering his life from youth and his student days at the University of Pennsylvania to his homecoming as an Army officer after the end of World War One in 1919. In the first year it sold more than 90,000 copies in America before it was published in England. The Rt. Hon. Leo Amery, M.P., commented that "My old friend Lloyd Griscom gives a delightfully breezy picture as seen through American eyes of Edwardian England, of the diplomatic world, of many countries."