Gillis Devery (died 1864) was an American dentist who lived in the Five Points section of Manhattan, New York City during the 1860s. The husband of Ethel Devery, he had several affairs with younger women, but, on learning of his wife's affair with the butcher Hans Elek, Gillis plotted to have him killed. He poisoned a fruit cake his wife had bought for Elek from Deroot Nellis, but Elek re-gifted the cake to his landlord Eugene Lunsford, who in turn re-gifted the cake to Devery, as he did not like fruit cake. Devery consumed the pastry, unaware that it was the same cake, and he died shortly after. The NYPD ultimately ruled his death an accident on determining that he had poisoned himself.