There has long been a connection between the concept of utopia as a perfect society and the desire for perfect humans to live in this society. A form of selective breeding takes place in many fictional utopias from Plato’s Republic onwards, but it is only with the naming and promotion of eugenics by Francis Galton in the late nineteenth century that eugenics becomes a consistent and important component of utopian fiction. In my introduction I argue that behind the desire for eugenic fitness within utopias resides a sense that human nature needs improving. Darwin’s Origin of Species (1859) prompted fears of degeneration, and eugenics was seen as a means of restoring purpose and control. Chapter Two examines the impact of Darwin’s ideas on the late nineteenth-century utopia through contrasting the evolutionary fears of Samuel Butler’s Erewhon (1872) with Edward Bellamy’s more positive view of the potential of evolution in Looking Backward (1888). Chapter Three uses examples from three late-nineteenth-century feminist utopias to highlight the aspirations within these societies to use science to transform women’s social position and transcend the biological determinism of their reproductive role. Chapter Four focuses on the social theory and utopian fiction of Charlotte Perkins Gilman to illustrate how eugenics becomes part of her vision of progress for women and the human race as a whole. Chapter Five turns to dystopian fiction from H.G. Wells, Aldous Huxley, Yevgeny Zamyatin, Charlotte Haldane and Katherine Burdekin to examine how eugenic ideas retained an element of idealism even in the context of the dystopias of the first half of the twentieth century. Chapter Six looks at the fate of eugenics in utopian fiction after the Second World War and argues that the resurgence of utopianism in the form of the ecological utopia continue to rely on eugenics, population control and manipulation of human behaviour to succeed. My conclusion argues that eugenics is a utopian idea with enduring appeal despite the disastrous effects of its practical implementation, and that utopian and dystopian fiction offer an important lens through which to understand the hopes and fears represented by the different versions of eugenics and the current debates over genetic enhancements and transhumanism.