The Inventory of Paintings of Cardinal Pietro Ottoboni (1667-1740) is the study of the inventory of more than 500 art works, assembled on the death of Cardinal Pietro Ottoboni who had been vice-chancellor of the Church for fifty years. The cardinal's commissions are distinguished from the 387 paintings inherited from his great-uncle, Pope Alexander VIII, in 1691. The cardinal's taste and patronage are characterized from approximately 100 works identified in modern collections. Other archival information, diary accounts, artists' biographies, testaments, and guidebooks are consulted for insights into the cardinal's collecting habits.