Valentina Pavlovna (Guercken) Wasson (1901 – 1958) was a Russian-American pediatrician, ethnomycologist and author. She was involved in the introduction of psychoactive mushrooms to a wide audience in the United States.

Born in Moscow in 1901, Valentina Pavlovna Guercken's family immigrated to the United States during the Russian Revolution. She earned a medical degree at London University in 1927, one year after she married her husband R. Gordon Wasson, a banker. She worked as a pediatrician, publishing research on sinusitis and rheumatic fever in children.

Described themselves as "ethnomycologists", Valentina and R. Gordon researched religious and cultural uses of fungi by sending letters to missionaries, linguists, and anthropologists around the world, trying to identify areas where mushrooms possessed significant religious and medical uses. With busy professional lives, the couple pursued the research as a passionate side project. Valentina and Gordon Wasson organized yearly research expeditions to the remote mountain villages of the monolingual Mazatec Indians of Oaxaca, Mexico, and in 1955 were among the first outsiders in modern times to participate in the midnight rites of the cult of the sacred mushroom.

They announced their discovery in 1957 in their jointly written book Mushrooms Russia and History. Concurrently, a lengthy illustrated article by R. Gordon in Life Magazine, May 13, 1957, on the Mexican mushroom veladas (sessions) with Maria Sabina brought significant attention to the use of hallucinogenic mushrooms. Wasson's account of this experience was published in This Week on May 19, 1957. In this article, Valentina suggested that Psilocybe mushrooms might be used as a psychotherapeutic agent.

Valentina Wasson died of cancer on December 31, 1958, at the age of 57. Following her death, Gordon continued their research, working closely with Roger Heim, a French mycologist and the director of the Museum National d’Histoire Naturelle, who had accompanied the Wassons on several expeditions to Mexico and provided determinations for the mycological samples they collected in Mexico.