Oisín McGann was born and raised in Dublin and Drogheda, County Louth, in Ireland. He studied art at Senior College Ballyfermot and Dún Laoghaire School of Art, Design & Technology. Before becoming an author, he worked as a freelance illustrator, serving time along the way as a pizza chef and a security guard, as well as a background artist for an animation company and an art director and copywriter in an advertising agency.
In 2003 McGann published his first two books in the Mad Grandad series for young readers, followed by his first young adult novel, The Gods and Their Machines. Since then, he has written several more novels for young adults, including the Wildenstern Saga, a steampunk series set in nineteenth-century Ireland, and the thrillers Strangled Silence and Rat Runners.
A full-time writer and illustrator, McGann is married, has three children, and lives somewhere in the Irish countryside.