Serge Abrahamovitch Voronoff (Russian: Сергей Абрамович Воронов; c. July 10, 1866 – September 3, 1951) was a French surgeon of Russian extraction who gained fame for his technique of grafting monkey testicle tissue on to the testicles of men for purportedly therapeutic purposes while working in France in the 1920s and 1930s. The technique brought him a great deal of money, although he was already independently wealthy. However, his theories remained controversial throughout his life, and he was often ridiculed by medical authorities over his claims. According to one contemporary newspaper, he was famously known as the "monkey gland man".