Thomas Walter Laqueur (born September 6, 1945) is an American historian, sexologist and writer. He is the author of Solitary Sex: A Cultural History of Masturbation and Making Sex: Body and Gender from the Greeks to Freud as well as many articles and reviews. He is the winner of the Andrew W. Mellon Foundation's 2007 Distinguished Achievement Award, and is currently the Helen Fawcett Distinguished Professor of History at the University of California, Berkeley, located in Berkeley, California. Laqueur was elected to the American Philosophical Society in 2015.

Laqueur wrote that there was an ancient "one-sex model", in which the woman was only described as imperfect man / human and he postulates that definitions of sex/gender were historically different and changeable.

This argument has been challenged by some historians of science and experts in Early Modernity, notably Katharine Park and Robert A. Nye; Monica Green, Heinz-Jürgen Voss, Helen King, and Paola Uparela, who reject the suggestion that ancient descriptions show a homogenous model, the one-sex model which then mutated in the 18th century to a two-sex model. They encourage a more differentiated perception that makes clear that gender theories of natural philosophy as well as biology and medicine, are embedded and constructed in certain social contexts.