Shakespeare used a handful of sources for Much Ado About Nothing.
Lodovico Ariosto, translated by Sir John Harington, Orlando Furioso (1591). Canto 5 of the poem provided Shakespeare with the marriage between Hero and Claudio and Don John’s plot to prevent it.
Matteo Bandello, La Prima Parte de le Nouelle(1554). The 22nd of Bandello’s novellas gave Shakespeare the setting in Messina, as well as contributing to the marriage plot involving Hero, Claudio, and Don John.
Matteo Bandello, translated by François de Belleforest, Le Troisiesme Tome des Histoires Tragiques Extraittes des Oeuvres Italiennes de Bandel (1569). Shakespeare could have used either Bandello’s Italian original or the translation and adaptation by Belleforest.
Baldassare Castiglione, translated by Sir Thomas Hoby, The Courtier (1588). This work was perhaps Shakespeare’s source for the romance between Beatrice and Benedick.