R.S. Thomas is one of the most important contemporary poets in Great Britain. The author of this study uses a twofold approach in order to sketch a portrait of his work. On the one hand, R.S. Thomas's historical and literary Welsh background with its particular problems of language and identity is delineated. On the other hand, groups of poems which focus on specific themes are analyzed extensively, so that the principles of the poet's thoughts and the development of his work from the 40s up to the present become transparent.