Robert Leslie Conly, better known by his pen name Robert C. O'Brien, was an American author and journalist for National Geographic Magazine. He is renowned for his imaginative and compelling works of fiction, often exploring themes of survival and courage. His notable works include "Mrs. Frisby and the Rats of NIMH," which won the 1972 Newbery Medal. O'Brien's legacy continues through his daughter, Jane Leslie Conly, who is also an acclaimed author.