John Field (26 July 1782, Dublin – 23 January 1837, Moscow) was an Irish pianist, composer, and teacher widely credited as the inventor of the nocturne. While other composers were writing in a similar style at this time, Field was the first to use the term 'Nocturne' specifically to apply to a character piece featuring a cantabile melody over an arpeggiated accompaniment.

He was born into a musical family, in Dublin, and received his early education there, in particular with the Italian composer Tommaso Giordani. The family moved to London in 1793, where Field studied under Muzio Clementi, and under whose tutelage Field soon became a famous and sought-after concert pianist. Together, master and pupil visited Paris, Vienna, and St. Petersburg. Ambiguity surrounds Field's decision to remain in the former Russian capital, but it is likely that Field acted as a sales representative for the Clementi Pianos.

Field was very highly regarded by his contemporaries and his playing and compositions influenced many major composers, including Frédéric Chopin, Johannes Brahms, Robert Schumann, and Franz Liszt. Although little is known of Field in Russia, he undoubtedly contributed substantially to concerts and teaching, and to the development of the Russian piano school.

Notable students include Prussian pianist and composer Charles Mayer, the Franco-Russian composer Alexandre Dubuque, and Polish pianist and composer Antoine de Kontski.