Steampunk, as a literary genre and cultural phenomena, is a relatively recent innovation that is increasingly receiving critical attention. From the proto-steampunk of Jules Verne and H.G. Wells, through the novels of its acknowledged founding fathers K.W. Jeter, Tim Powers and James Blaylock, to contemporary works by China Miéville, Cherie Priest and Paul Di Filipo, steampunk has been plagued by the lack of a unifying definition. Every author, academic and critic has their own definition of it, which may share similarities with others, but none of them can agree on the core ingredients of the genre. Related to the important task of defining steampunk is the need to answer the question: 'Is steampunk a literary genre?' In many respects, steampunk has moved beyond the literary world. Fashion, art and sub-cultures have all embraced steampunk as a style, an aesthetic, a way of life and even a philosophy. This could be the reason for the inability to find a single unifying definition of steampunk. This thesis will argue that, rather than a genre, steampunk is best understood as an aesthetic which can be applied, like any aesthetic, to any literary genre to produce a work that is steampunk-inflected, such as science fiction steampunk, alternate history steampunk, steampunk fantasy, historical steampunk, steampunk romance or gothic steampunk. After evaluating both scholarly and popular definitions of steampunk I will explore four key aspects of the steampunk aesthetic: the neo-Victorian tropes which dominate steampunk texts; the relationship between magic and science in the steampunk universe; the places and people who inhabit steampunk worlds; and the revolutionary message of most steampunk creations. Throughout my discussion will focus primarily on a range of texts acknowledged as steampunk: Michael Moorcock’s The Warlord of the Air (1971), K. W. Jeter’s Infernal Devices (1987), Tim Powers’ The Anubis Gates (1983), William Gibson and Bruce Sterling’s The Difference Engine (1991), Paul Di Filippo’s The Steampunk Trilogy (1995), Neal Stephenson’s The Diamond Age (1995), Gail Carriger’s ‘Parasol Protectorate’ series (2009 – current), Mark Hodder’s ‘Burton and Swinburne’ series (2010 – current), Arcanum: Of Steamworks and Magick Obscura by Troika Games and Runic Games’ Torchlight (2009) and Torchlight 2 (2011).