This surname project is open to anyone of any gender willing to work together, sharing family trees and DNA results, to explore the origins of our Harrigan/Horrigan/Hourigan/spelling-variant ancestors. The data collected and analyzed in this project is limited to Y-DNA test results (minimum 37 markers) stored at FamilyTreeDNA. These tests are taken by men whose direct patrilineal ancestor was a Harrigan/Horrigan/Hourigan/related spelling variant. Autosomal and Mitochondrial DNA test results are not in scope. The map in the banner shows the location of 19th century heads of households in Ireland with the surname of Horrigan or variants. This map was created by John Grenham, “Irish Surnames,” Irish Ancestry, search for Horrigan and variants (https://www.johngrenham.com/findasurname.php?surname=horrigan&search_type=variants : accessed 3 Feb 2022). An external website supporting this surname project is available at https://sites.google.com/view/harrigan-horrigan-hourigan/home.