The purpose of my dissertation is to explore Darwinian influence on Thomas Hardy's fiction and poetry. It is divided into seven chapters. In the first chapter, the definition of Darwinism is given in its recent reincarnation which took place in the 1970s, and the parallel history between studies of Darwinism and Hardy's literature is shown. In the second chapter, Hardy is discussed in a literary context that includes some contemporary evolutionary intellectuals such as Zola, Henry James, and readers under the strong impact of Darwinism. Hardy's concept of outer and inner or human nature is expanded by Darwinism. In the third and fourth chapters, his works are explored in terms of this concept, with special attention to sexual love in contrast with loving-kindness in human nature. In the fifth chapter, the ethnical implication of evolutionary theories in his major later novels, The Return of the Native, The Mayor of Casterbridge, The Woodlanders, Tess of the d'Urbervilles and Jude the Obscure are discussed in terms of the Greek classical tradition. Special attention is paid to the ethical debate caused by the Darwinian concept of humans, namely the controversy between intuitive theory and utilitarianism. This refers to Herbert Spencer and Thomas Henry Huxley, who were deeply influenced by Darwin. In the sixth chapter, an account is given of the theme of non-teleology of Darwin's natural selection in The Well-Beloved, with reference to heredity in Platonic ideas, and that of time in his poems and epic-drama, The Dynasts. In the seventh chapter, Hardy's struggles to recover from the upsetting impact of Darwinism is explored in this elegiac "The Poems of 1912-13." In these and other poems, Hardy expanded and deepened his classically conceived art and revitalized the traditional ethnical concept of loving-kindness, which is supported by Darwinian theory of common descent. My conclusion is that Hardy's intellectual, ethnical, and literary struggles were productive and original enough to make a major contribution to English traditional literature, which paved the way for new literature in the twentieth century. In the appendix, the important dates of European literature and evolutionary theory are chronologically shown.