François-Joseph Fétis (French: [feti]; 25 March 1784 – 26 March 1871) was a Belgian musicologist, composer, teacher, and one of the most influential music critics of the 19th century. His enormous compilation of biographical data in the Biographie universelle des musiciens remains an important source of information today. His wife, Adélaïde Robert, was the daughter of the French politician Pierre-François-Joseph Robert.
Fétis was born in Mons, Hainaut, and was trained as a musician by his father, who followed the same calling. His talent for composition manifested itself at the age of seven, and at nine years old he was an organist at Sainte-Waudru, Mons.
In 1800 he went to Paris and completed his studies at the Conservatory under such masters as Boïeldieu, Jean-Baptiste Rey and Louis-Barthélémy Pradher.
In 1806 he undertook the revision of the Roman liturgical chants in the hope of discovering and establishing their original form. In this year he also began his Biographie universelle des musiciens, the most important of his works, which did not appear until 1834.