The 3rd International Workshop on Gallium Oxide and Related Materials (IWGO-3) is the premier international forum for high impact research on gallium oxide and related materials. The 2019 Workshop took place from August 12-15 on the campus of The Ohio State University (OSU) in Columbus, Ohio, and was held in a single-session format to allow for maximum interaction between researchers of various technical disciplines. It also included a special session for the U.S. Workshop on Gallium Oxide (GOX) highlighting U.S.-funded basic research efforts.