The Ianua Indica (Indian Gateway) of Ignazio Arcamone S.J. (ca. 1615–1683) is the first comparative grammar of two South Asian vernaculars, Konkani and Marathi. This volume offers a critical edition of the Latin original based on the two surviving manuscripts, a translation into English, and a selection of extracts from sources that shed light on its genesis and significance, including part of an unpublished text by the British orientalist John Leyden (1775–1811) entitled “Plan for Investigating the Languages, Literatures, Antiquities and History of the Deccan.” It also features an extended introduction to this forgotten milestone in the history of Indology that outlines Arcamone’s reliance on the techniques of “Jesuit world philology” and the intellectual formation of the author in Italy and India.