Isaac Leonard Ellwood (August 3, 1833 – September 11, 1910) was an American rancher, businessman and barbed wire entrepreneur.

[1] Ellwood found some success in California and returned east in 1855, to DeKalb, Illinois, where he opened a hardware and implements store.

This prompted Ellwood along with other DeKalb area residents Jacob Haish and Joseph Glidden to work on improving the concept.

Ellwood patented a type of barbed wire in February 1874, but ever the businessman, concluded that Joseph Glidden's design was superior to his.

Ellwood's hiring of John Warne Gates as a salesman propelled sales of barbed wire in Texas.

Clinton Rosette helped persuade Ellwood that the new Northern Illinois State Normal School should be in DeKalb.

[6] Governor John Altgeld appointed Ellwood to the Board of Trustees, who were responsible for selecting a site for the normal school.

[6] On a business trip to Texas in 1886, he purchased the 130,000 acre (530 km²) in Mitchell County from John and Dudley Snyder.