Aroldo is an opera in four acts by Giuseppe Verdi to an Italian libretto by Francesco Maria Piave, based on and adapted from their earlier 1850 collaboration, Stiffelio. The first performance was given in the Teatro Nuovo Comunale in Rimini on 16 August 1857.

Stiffelio had provoked the censorship board because of “the immoral and rough” storylines of a Protestant minister deceived by his wife and also because making the characters German did not please an Italian audience, although, as Budden notes, the opera "enjoyed a limited circulation (in Italy), but with the title changed to Guglielmo Wellingrode, the main protagonist now a German minister of state". Verdi had rejected an 1852 request to write a new last act for the Wellingrode version, but, by Spring 1856, in collaboration with his original librettist, Piave, he decided to rewrite the story line and make a small amount of musical changes and additions. However, as it turned out, the work was to be more complex than that.

Drawing inspiration from novels of Edward Bulwer-Lytton (Harold: the Last of the Saxon Kings - for the location of the opera to England and Scotland (in the last act) in the Middle Ages and for the names of its characters, the principal being Aroldo, re-cast as a recently-returned Crusader.) Kimbell notes that "hints" came from the work of Walter Scott whose novel of 1825, The Bethrothed would "already have been familiar to Italian audiences through Giovanni Pacini's 1829 opera, Il Contestabile di Chester". Also, the novelist's The Lady of the Lake was the inspiration for the hermit Briano.

The rewriting was delayed until after March 1857 by the preparation for Paris of Le trouvère, the French version of Il trovatore, and his work with Piave on Simon Boccanegra. However, as work resumed on Aroldo with Piave, the premiere was planned for August 1857 in Rimini. When Verdi and Strepponi arrived there on 23 July, they found both Piave and Angelo Mariani (with whom he had become friends over the previous years and who had been chosen to conduct the new opera) working together. While Phillips-Matz notes that there was "hysteria" at Verdi's presence, there was also opposition to Aroldo combined with an influx of people from other cities anxious to see the new opera. With Mariani, rehearsals began well; the conductor reported: "Verdi is very very happy and so am I".

By the time of the premiere, considerable changes had been made to the three-act Stiffelio, the prime one being an added fourth act with new material, described by conductor Mariani to Ricordi as "a stupendous affair; you'll find in it a storm, a pastoral chorus, and an Angelus Dei treated in canon and beautifully wrought". Lina became Mina; Stiffelio, as discussed, was now Aroldo; Stankar morphed into Egberto; Jorg, the bass role, emerged as Briano.