Guerdon Saltonstall Trueblood (November 2, 1933 – March 3, 2021) was a Costa Rican-born American screenwriter, producer, director and actor.

Trueblood was born in San Jose, Costa Rica to Edward Gatewood Trueblood (1905-1994) and Elizabeth (1906-1973), daughter of United States Army general and aviator Billy Mitchell. He had an elder sister, Felicity (1932-2021).^[1][2][3] Edward Trueblood was a Princeton-educated diplomat assigned to Asuncion, Santiago, and Paris,^[4][5] and would later serve as a UNESCO cultural relations officer in Uruguay and India, and as permanent U.S. representative to UNESCO stationed in Paris; he was also a senior editor of the Encyclopædia Britannica, and an associate professor of Latin American Studies in Phoenix, Arizona.^[6] The Trueblood family had been resident in America since 1682, being descendants of John Trueblood, of Shoreditch, London, England.^[7]

At age eight, his parents having divorced in 1940,^[8] Trueblood went to live with his grandparents in Alexandria, Virginia. After serving in the United States Navy as a sonar technician, he attended George Washington University, majoring in speech and drama, then lived in Provence, France before moving to Hollywood in 1969.^[9]

Trueblood co-wrote, with Richard Matheson, Jaws 3D (1983);^[10] and Sole Survivor (1970), directed by Paul Stanley and starring Vince Edwards, Richard Basehart and William Shatner.^[11] He directed the cinematography of Hollywood Meat Cleaver Massacre (1976),^[12] where he also played the nuthouse doctor starring Christopher Lee.^[13]

He created, produced and wrote Bravo Two (1977), directed by Ernest Pintoff.^[14] He directed The Candy Snatchers (1973), written by Bryan Gindoff and produced by Marmot Productions.^[15]

In 1964, Trueblood married Anne-Marie ("Anna") Vaughan Read, who predeceased him; they had two sons- visual effects artist^[16] Guerdon jr, and Christopher- and a daughter, Alexandra.^[17] Trueblood died on March 3, 2021, in Sister Bay, Wisconsin, at the age of 87.^[18][19]