Despite his role as a founder of English Romanticism, Coleridge remains a comparatively obscure figure due to his dual nature as a great poet and a critic with challenging philosophies. Therefore, Biographia Literaria and Coleridge''s Poetry: Critical Thought in Poetic Language analyses Coleridge''s major poetic concepts in his critical work Biographia Literaria - that is, the concepts of imagination, the merging of subject and object, and the reconciliation of opposite or discordant qualities - and reveals how Coleridge''s poems reflect these concepts. After an introduction on Romanticism and Biographia Literaria, the work studies the concepts through critical views and concentrates on Coleridge''s poems "The Eolian Harp", "Kubla Khan", The Rime of the Ancient Mariner, and "Dejection: An Ode" to illustrate the argument. So, the study highlights Coleridge''s less-discovered critical side alongside his well-known nature as a talented poet. With such a deep analysis between Coleridge the Romantic critic and Coleridge the Romantic poet, Biographia Literaria and Coleridge''s Poetry aims to contribute to a comparatively unexplored area within the Romantic poetry studies.