This article publishes the 'Martyrdom of Saint Peter' painted by Carlo Sellitto in 1610-1612 for the chapel of the Cortone brothers in the old Neapolitan church of Sant'Anna dei Lombardi, of which, until now, only the 'Saint Peter saved from drowning' and the 'Delivery of the keys to Peter', preserved in Santa Maria di Monteoliveto in Naples, were thought to have survived. The article reconstructs the history of the painting, which entered the collections of the Bourbons in the early 19th century, was later jointly owned by Nicolao Cerù from Lucca and Gaetano Negretti from Como, and finally entered the Quadreria dell'Ospedale Sant'Anna in Como in 1890, where it still is today. In addition to placing the painting in Sellitto's artistic career, side by side with the other canvases painted by the artist for the Cortone chapel, the Quadreria dell'Ospedale Sant'Anna, little known to scholars, is briefly considered, with a mention of certain paintings that would deserve greater consideration, such as the 'Portrait of Galeazzo I Visconti', most probably from the Paolo Giovio Museum.