This essay discusses the Latin term ingenium within the writings of Francis Bacon (1561–1626). It proposes that although ingenium does not easily translate into English, Bacon uses the term in a clearly defined range of senses. For the most part, he echoes the discourse of ingenuity and inventiveness common to many sixteenth-century humanists, but differs from them in sharply delimiting the scope and status of ingenious thinking. In particular, he excludes ingenuity from the logical portion of his reformed art of discovery: as the goal of this was demonstrative knowledge, Bacon (like the Aristotelian logicians he aimed to supplant) believed that it had to be the province of the intellect, not of ingenium. A fuller understanding of the ways in which Bacon uses ingenium casts his methodological thought into illuminating new relief, and draws attention to the manner in which Bacon’s ideas were appropriated, criticized, and misunderstood in the half century after his death — not least by the self-styled Baconians in and around the early Royal Society.