Previous considerations of Freud's 1910 pathography of Leonardo da Vinci have grappled mainly with errors of fact (among them a mistranslation in the study's signature childhood memory, widely known since the 1950s). Here a more consequential flaw is examined: Freud's fatefully pathogenic framing of Leonardo's homosexuality. While few present-day analysts share that perspective in its entirety, Freud's complex and plausible reconstruction drew wide support in the literature for more than a century and has to date never been subjected to rigorous critique. A close reading of the study, exploring Freud's perspective and that of later psychoanalysts and historians, seeks to account for the biography's tenacious grip on the psychoanalytic imagination. In the end, it is argued, the pathography is a failed effort to grapple with an unsettling transformation unfolding around and within Freud: the emergence of the category that eventually would be called the “healthy homosexual.”