Robert Leslie Carroll Conly, better known by his pen name Robert C. O'Brien, was an American novelist and a journalist for National Geographic magazine. He is best known for his 1971 children's novel Mrs. Frisby and the Rats of NIMH, which was adapted to the 1982 animated film The Secret of NIMH directed by Don Bluth.

Mrs. Frisby and the Rats of NIMH is a 1971 children's science fiction/fantasy book by Robert C. O'Brien, with illustrations by Zina Bernstein. The novel was published by the Los Angeles publishing house Atheneum Books.