The libretto is based on Lockroy's and Edmond Badon's Un duel sous le cardinal de Richelieu, which was also the source of Donizetti's 1843 opera Maria di Rohan, although the setting for Giordano's version was moved from 17th-century Paris to 18th-century Naples.

[1] Regina Diaz was Giordano's second full-length opera and like its predecessor, Mala vita, was commissioned by the Milanese music publisher Edoardo Sonzogno.

Mala vita had had considerable success apart from its performances in Naples where the gritty verismo story and depiction of Neapolitan slum-dwellers had caused a furor amongst the critics and audience alike.

For his second opera, Sonzogno commissioned Giovanni Targioni-Tozzetti and Guido Menasci (the librettists of Mascagni's hugely successful Cavalleria rusticana) to write a libretto for Giordano.

The result was an old-fashioned romantic melodrama based on the same story used in Donizetti's Maria di Rohan but with the setting changed from 17th-century Paris to Naples in the early 18th century when it was under Spanish rule.

Regina Diaz premiered on 5 March 1894 at the Teatro Mercadante in Naples with the Spanish-born soprano Concepció "Concetta" Bordalba in the title role.

[6][7] Setting: Naples c. 1700[8] Act 1 Mario Sanseverino, a Neapolitan nobleman and leader of a rebellion against Spanish rule, approaches the friar Benedetto in the courtyard of a monastery.