Lucius Quintus Cincinnatus Lamar II, American jurist and politician, 16th United States Secretary of the Interior (died 1893)

Lucius Quintus Cincinnatus Lamar II was a Confederate soldier, American politician, diplomat, and jurist. A member of the Democratic Party, he represented Mississippi in both houses of Congress, served as the United States Secretary of the Interior, and was an associate justice of the Supreme Court of the United States. He also served as an official in the Confederate States of America.

The United States secretary of the interior is the head of the United States Department of the Interior. The secretary and the Department of the Interior are responsible for the management and conservation of most federal land along with natural resources, leading such agencies as the Bureau of Land Management, the United States Geological Survey, the Bureau of Indian Affairs and the National Park Service. The secretary also serves on and appoints the private citizens on the National Park Foundation Board. The secretary is a member of the United States Cabinet and reports to the president of the United States. The function of the U.S. Department of the Interior is different from that of the interior minister designated in many other countries.