Mangelia hancocki is an extinct species of sea snail, a marine gastropod mollusc in the family Mangeliidae. This fossil was discovered in the Galapagos Islands by Leo George Hertlein (1898 – 1972) and (1876 - 1951), who were there as a part of the Valero III's voyage to the tropical eastern Pacific. It was named for Captain G. Allan Hancock, the owner and captain of the Valero III. There are only two known collections of this species, both by Leo George Hertlein.