Thurston Howell III (mentioned in the opening credits as: "The Millionaire") is a character on the CBS television sitcom Gilligan's Island, which ran from 1964 to 1967, and later in syndication.

Howell, portrayed by veteran character actor Jim Backus, took hundreds of thousands of dollars in cash and several changes of clothing with him for what was intended to be only a three-hour boat tour in Hawaii.

Speaking with a Locust Valley lockjaw accent, Howell is a stereotypical member of the New England Yankee elite – a resident of Newport, Rhode Island, a graduate of Harvard University and a Republican.

Among his assets were a diamond mine, a coconut plantation, a railroad, an oil well, and 40 acres (16 ha) in Colorado – which included all of downtown Denver – that he bequeathed to his fellow castaways in his will.

When he hears that an imposter is going to sell off his companies for cash, he is so enraged that he tries to swim back to the mainland three times, intent on killing the man, only to be stopped by Gilligan, the Skipper, and wife Lovey.