Frank Merrill Caldwell (November 8, 1866 – March 8, 1937) was a career United States Army officer who served as a brigadier general during World War I and earlier served as a lieutenant colonel in the Spanish–American War.

His classmates at the USMA included Colden Ruggles, Fred W. Sladen, William J.

Snow, Clint C. Hearn, Daniel W. Ketcham, Edgar Jadwin, Francis Marshall, Harry H. Bandholtz, Henry D. Todd Jr., William C. Davis, George G. Gatley, William S. McNair and Herbert Deakyne.

[3][4] During the Spanish–American War, he served as lieutenant colonel of the 4th Wisconsin Infantry Regiment, but was removed from volunteer service in 1899.

[3] Caldwell died at the age of seventy on March 8, 1937, in San Francisco, California.