Mark Clifton (1906 - 1963) was an American author and businessman.
He wrote science fiction and most of his stories fit into one of two series. The "Bossy" sequence, was written alone and in collaboration with both Alex Apostolides and Frank Riley. The "Ralph Kennedy" series, which is lighter in tone was mostly written solo, although there was one collaboration with Apostolides. Clifton gained his greatest success with his novel What Have I Done?"