ABSTRACT This article reads Coleridge’s “The Rime of the Ancient Mariner” of 1798 as a visionary speculation on the ground-breaking technologies of its time—the steam engine and early experiments with steamboats. Within the larger framework of a history of the Anthropocene and drawing, more specifically, on science studies, current eco-Marxist perspectives and earlier (new) historicist research, I show how the poem blends two distinct epistemic frameworks and temporalities that have been neglected in critical discussions. On the one hand, Coleridge’s text resonates with the earlier mechanical philosophy and imagery from Thomas Burnet’s Sacred Theory of the Earth (1684/90) which expounds a natural history featuring engines; on the other hand, it negotiates contemporary experiments with steam transport and James Watt’s patented improvement of the steam engine, in particular. Intimating an acceleration of (natural) history through human technology, the poem, I argue, displays a powerful and highly ambivalent sense of that acceleration’s social, colonial, and ecological entanglements. By way of conclusion, the article considers the afterlife of the “Rime” in Coleridge’s letters, and in Victorian engineering discourse; I showcase the poem as a spectacular and self-reflexive example of early speculative (or science) fiction.