‘we breathe naphthalene air, the pillars of smoke writhe and the astringent sky lies pale at her sides’: this line in Lynette Roberts’ 1941 poem ‘Swansea Raid’ – its speaker located 20 miles up the coast - registers the dramatic effects of the Luftwaffe’s bombing of oil infrastructure in south Wales. The Llandarcy oil refinery in Swansea, founded in 1921 by Anglo-Persian, was the UK’s first, and was one of a number of oil industry installations in south Wales – including the Angle Bay oil terminal in Milford Haven, its 46-mile pipeline to Llandarcy, the Baglan Bay petrochemical site near Port Talbot, and the chemical plant in Barry, near Cardiff. While Anglophone Welsh literature is usually associated with the coal industry, this paper begins to set out a historically-neglected tradition of Welsh petrofiction. There are texts of oil-encounter modernization: texts which register the impact of the oil industry in south Wales between 1921 and the closure of the sites in the 1990s and 2000s.. More subtly, and following Mark Bould’s concept of the Anthropocene Unconscious, this paper identifies petrofiction in texts which depict the devastation of communities in Welsh coal producing areas - following the ‘turn to oil’ in the third and fourth decades of the twentieth century and the ‘Great Acceleration’ in the aftermath of the Second World War. Finally, the paper identifies some modern and contemporary Welsh fiction which registers the increasing presence in our lives of products that come from the process of oil extraction.