Ellen McArthur was one of the earliest students of Girton College, Cambridge. Although excluded from full membership of Cambridge University (women were only admitted as faculty members in 1926, and as students in 1948), she went on to pioneer the new field of academic history and to teach in Cambridge for a quarter of a century, as well as at the newly formed London School of Economics in the 1890s and at Westfield College in London. McArthur campaigned tirelessly for suffrage and to admit women to Cambridge University, while teaching an entire generation of women university historians, ranging from medievalists to modernists. This article examines her intellectual and political context and influence.