Nicolas-François Guillard (16 January 1752 – 26 December 1814) was a French librettist. He was born in Chartres and died in Paris, the recipient of a government pension in recognition of his work writing librettos. He was also on Comité de Lecture of the Paris Opéra. One of the foremost of the French librettist of his generation, he wrote libretti for many noted composers of the day, including Salieri (Les Horaces) and in particular Sacchini (Œdipe à Colone, amongst many others). His most famous work is Iphigénie en Tauride, his first libretto, set by Gluck after the composer had initially rejected it. Gluck collaborated with Guillard to heavily recast the libretto, not only to suit Gluck's artistic preferences, but also to accommodate pre-existing music that Gluck borrowed, both from himself and from other composers, when composing the opera.
Guillard's librettos were often adaptations of previously written works, rather than the products of original invention. He used a wide range of subjects as a starting point, basing his libretto for Sacchini's final opera, Arvire et Évélina, on an English dramatic poem and also using the works of Pierre Corneille on two occasions. In the 1790s he altered his style to fit the revolutionary atmosphere of the time, one of his last works being the epic La mort d'Adam, where he turned to biblical themes.