Ole Ivar Lovaas (1927-2010) is known worldwide for his research within the field of Applied Behavior Analysis, and is probably the most influential researcher within the field of treatment of children with autism. In the first part of this biographically oriented paper, we inform the readers about his family background, childhood, elementary and secondary school years, and his adolescent years during World War II in his first homeland, Norway, based on archival research and interviews. In the second part, we describe his life, academic studies, research and successes in his second home country, the United States. Finally, we briefly recount the impact Lovaas has had on the field of Applied Behavior Analysis and the treatment of and services for children with autism spectrum disorders in Norway and in the North America.