Háry János is a Hungarian folk opera (that is, a spoken play with songs, in the manner of a Singspiel) in four acts by Zoltán Kodály to a Hungarian libretto by Béla Paulini (1881–1945) and Zsolt Harsányi, based on the comic epic The Veteran (Az obsitos) by János Garay. The first performance was at the Royal Hungarian Opera House, Budapest, 1926. The sub-title of the piece is Háry János kalandozásai Nagyabonytul a Burgváráig – János Háry: his Adventures from Nagyabony (Great Abony) to the Vienna Burg. The UK stage premiere was at the Buxton Festival in 1982 conducted by Anthony Hose with Alan Opie in the title role.

The story is of a veteran hussar in the Austrian army in the first half of the 19th century who sits in the village inn regaling his listeners with fantastic tales of heroism (in the tradition of Miles Gloriosus). His supposed exploits include winning the heart of the Empress Marie Louise, the wife of Napoleon, and then single-handedly defeating Napoleon and his armies. Nevertheless, he finally renounces all riches in order to go back to his village with his sweetheart.

Kodály wrote in his preface to the score: "Háry is a peasant, a veteran soldier who day after day sits at the tavern spinning yarns about his heroic exploits... the stories released by his imagination are an inextricable mixture of realism and naivety, of comic humour and pathos." He also comments that "though superficially he appears to be merely a braggart, essentially he is a natural visionary and poet. That his stories are not true is irrelevant, for they are the fruit of a lively imagination, seeking to create, for himself and for others, a beautiful dream world." Háry János embodies the poetic power of folklore to go beyond political frustrations; Kodály intended to bring his national folk music to an operatic setting.

The opera, and the suite, begin with an orchestral 'musical sneeze', best explained in Kodály's own words: "According to Hungarian superstition, if a statement is followed by a sneeze of one of the hearers, it is regarded as confirmation of its truth. The Suite begins with a sneeze of this kind! One of Háry's group of faithful listeners … sneezes at the wildest assertions of the old tale-spinner."