This chapter defines the author's term solastalgia as the lived experience of negative environmental change. The origins of this concept are explained via an account of the impact of coal mining in the Upper Hunter Valley of New South Wales in Australia. The derivation of solastalgia from nostalgia (homesickness) and other roots is explained. The original research base of solastalgia is described as are the many applications of the concept world-wide over the last fifteen years since its creation. The applications of solastalgia are examined in academic, popular and cultural contexts, including the domain of ecocriticism. The chapter also considers some critical reflections on the concept since its creation.