Thomas Lincoln Casey Sr. (May 10, 1831 – March 25, 1896) was a noted American military and civil engineer of the late 19th century. He served as Chief of Engineers for the United States Army Corps of Engineers and oversaw the completion of the Washington Monument. American engineer Richard Weingardt wrote that Casey was the "U.S. Army Corps of Engineers’ most visible and celebrated builder of public buildings, monuments, and other significant works in the latter part of the 19th century."