This article presents the text of a treatise on the beylerbeylik of Rumeli, written by Antonio Bruni in 1596, and gives a summary account of Bruni’s life. Bruni was an Albanian from the Venetian-ruled city of Ulcinj; members of his extended family worked in Venetian, papal and Ottoman service, and he himself, after a Jesuit schooling in Rome and a doctorate in Avignon, worked for one of his cousins in Moldavia. His treatise was written for Cardinal Cinzio, nephew of Pope Clement VIII, at a time when the Papacy had a strong interest in exploiting Ottoman military weakness and encouraging rebellion, particularly in the Albanian lands. Bruni’s work shows a detailed knowledge of conditions both in Rumeli generally and in Albania. This treatise, which has remained unknown in modern times, has a double significance: it is the first general description of Albania by a named Albanian author, and it was also a major source of information for Lazaro Soranzo’s L’Ottomanno (1598), one of the most influential early modern publications on the Ottoman Empire.