Gregor Joseph Werner (28 January 1693 – 3 March 1766) was an Austrian composer.
Werner was born in Ybbs an der Donau. He served from 1715 to either 1716 or 1721 (unknown) as the organist at Melk Abbey. During the 1720s he was in Vienna, where he may have studied with Johann Fux. Werner was married on 27 January 1727.
On 10 May 1728 he took up the position he was to hold for the rest of his life, as Kapellmeister at the Esterházy court in Schloss Esterházy in Eisenstadt. The appointment "opened a new era for music" at the court; previously, there had been seven years of relative inactivity following the death of Prince Joseph in 1721; his widow Maria Octavia, serving as co-regent for her young son Paul Anton, had instituted economies in the musical establishment.Robbins Landon and Jones suggest that Werner was hired at the then 17-year-old prince's instigation.
Werner set to work, bringing new music to the court from Vienna and composing prolifically. He remained in full charge of the Esterházy musical establishment until 1761, when he entered a period of semi-retirement, his responsibilities limited to church music. Throughout this time he worked for a prince who was himself highly musical: Paul Anton had received musical training from the court musicians as well as from music masters imported from abroad; he played the violin and the flute.
Werner died in Eisenstadt on 3 March 1766.
Werner wrote a cappella masses in a strict contrapuntal style, as well as church music with instrumental accompaniment and symphonies. His work includes a series of twenty oratorios, all composed for performance on Good Friday, usually in the Esterházy chapel. Jones discerns a bifurcated style, with most of the work taking the form of severe, "weighty" contrapuntal pieces, but a minority (written for lighter occasions such as Advent and the Nativity) that "employ a distinctly homespun idiom, invoking elements of Austrian and indeed Eastern European folk music." Works by Joseph Haydn in both genres exist, and may have been influenced by Werner.