Donizetti"s moving and tragic opera Dom Sébastien, a full five-act grand opéra, was his last and perhaps most ambitious project. He had taken Paris by storm in previous years with a volley of triumphs and planned Dom Sébastien as an impressive and innovative artistic statement. Yet the project was plagued by demands for cuts and alterations during the rehearsal period. While the 1843 Paris premiere was a success, the dissatisfied composer made several changes for the opera"s 1845 Vienna premiere. For the 1847 Milan production, however, changes and misreadings generated an altered version in Italian—the version commonly known today—and Donizetti"s failing health prevented his involvement then or later. Recent musicological speculation about this distorted version has generated further misunderstanding.This new critical edition of Dom Sébastien clears up the years of confusion by restoring the original French text as Donizetti planned it. This edition contains commentary in English. Appendixes include his variants from the 1845 Viennese production, most notably the new ensemble piece added to the finale of the third act. This score provides scholars and musicians with a definitive edition of Donizetti"s last great masterwork.