Scholarship has slowly come to recognise that the Greek treatise Περὶ ὕψους or On the Sublime ascribed to Longinus was more widely disseminated in the seventeenth century than was once thought. In this article I present a previously unstudied seventeenth-century English translation of Longinus, comprising approximately a quarter of the whole treatise, found in the Lansdowne collection of the British Library. After assessing the manuscript and its provenance, I attempt to determine the edition used for the translation, settling on the 1636 Oxford edition of Gerard Langbaine as the most likely candidate. I then consider the approach of the translator and, following some remarks on the date and authorship of the manuscript, provide a semi-diplomatic transcription of the text.