Juan Crisóstomo Jacobo Antonio de Arriaga y Balzola (January 27, 1806 – January 17, 1826) was a Spanish composer. He was nicknamed "the Spanish Mozart" after he died, because, like Wolfgang Amadeus Mozart, he was both a child prodigy and an accomplished composer who died young. Whether by design or coincidence, they also shared the same first and second baptismal names; and they shared the same birthday, January 27 (fifty years apart).

Juan Crisóstomo Arriaga was born in Bilbao, Biscay, on what would have been Mozart's fiftieth birthday. His father and older brother first taught him music. He then studied the violin under Pierre Baillot, counterpoint with Luigi Cherubini and harmony under François-Joseph Fétis at the Paris Conservatoire. He was so talented that he soon became a teaching assistant in Fétis's class. He died in Paris at the age of nineteen, of a lung ailment, or exhaustion, perhaps both.

Arriaga's music is "elegant, accomplished and notable for its harmonic warmth" (New Grove Concise Dictionary of Music). His greatest works are undoubtedly the three string quartets, which (like his predecessors D. Scarlatti, Soler and Boccherini) contain notably Spanish ethnic rhythmic and melodic elements, especially in the galloping 6/8 finale of No. 1 in D minor and the meditative second (slow) movements of No. 2 in A major (an impressive set of variations in D major taking off from the slow D major variation movements in Mozart's K. 464 and Beethoven's Op. 18 No. 5, which climaxes in a D minor variation even more passionate than Mozart's D minor variation in K. 464, in the form of an impassioned, plangent lament on the top two strings of the viola going up to the second A above middle C) and No. 3 in E-flat major (a tender G major lullaby for the newborn Christ child). Periodwise, his style is on the borderline between late Classicism and early Romanticism, ranging from the late Classical idiom of Mozart to the proto-Romanticism of early Beethoven.

According to Grove, Arriaga's death "before he was 20 was a sad loss to Basque music." Following his early death, with the only reliable biographical material being some reports by Fétis, his life story was fictionalized to play into rising Basque nationalism. A public theatre in his home city of Bilbao carries his name.