Cyrus Hall McCormick (February 15 1809 - May 13, 1884) of Virginia was an Irish American farmer, inventor, businessman, marketer and newspaper editor. He became famous as the inventor of the mechanical reaper in 1831. He moved to Chicago, Illinois, and was the founder, with his brothers Leander and William, of the McCormick Harvesting Machine Company which became part of International Harvester Corporation in 1902.

He was born at Walnut Grove, his family farm in Rockbridge County, Virginia, in the Shenandoah Valley on the western side of the Blue Ridge Mountains. The McCormick family farm near Raphine became a test farm for the school known as Virginia Polytechnic Institute and State University (better known as "Virginia Tech").

Cyrus McCormick's father, Robert Hall McCormick, invented numerous labor-saving devices for agricultural use, and by 1831 had produced what would become known as the reaper. Robert's wife, Polly, encouraged Robert to give his inventions as a gift to their assertive and business-minded son, Cyrus, and encourage him to make the most of it. The reaper was demonstrated in tests in 1831 and was patented by Cyrus in 1834.