Ferdinand Ries (28 November 1784 (baptised) – 13 January 1838) was a German composer. Ries was a friend, pupil and secretary of Ludwig van Beethoven. He composed eight symphonies, a violin concerto, eight piano concertos and numerous other works in many genres, including 26 string quartets. In 1838 he published a collection of reminiscences of his teacher Beethoven, co-written with Franz Wegeler. The symphonies, some chamber works—most of them with piano— his violin concerto and his piano concertos have been recorded, demonstrating a style which is, unsurprising due to his connection to Beethoven, somewhere between those of the Classical and early Romantic eras.
Ries was born into a musical family of Bonn. His grandfather, Johann Ries (1723–1784), was appointed court trumpeter to the Elector of Cologne at Bonn.

The French dissolved the Electoral court of Bonn and disbanded its orchestra, but in the early months of 1803 the penniless Ries managed to reach Vienna, with a letter of introduction to Beethoven, who had received some early instruction at Bonn from Ries's father, Franz Anton Ries. Beethoven took great care of the young man, teaching him piano, sending him to Albrechtsberger for harmony and composition and securing for him positions as piano tutor in aristocratic households in Baden and Silesia. Ries made his public debut as a pianist in July 1804, playing Beethoven's C minor concerto, Op. 37, with his own cadenza, to glowing reviews.

Ries worked for Beethoven as secretary and copyist, winning Beethoven's confidence in negotiations with publishers and becoming a fast friend. One of the most famous stories told about Ries is connected with the first rehearsal of the Eroica Symphony, when Ries, during the performance, mistakenly believed that the horn player had come in too early and said so, aloud—infuriating Beethoven.[a]

Ries feared conscription in the occupying French army (though he was blind in one eye) and fled Vienna in September 1805. He spent two years in Paris before returning to Vienna, then concertized his way about Europe, landing in London in 1813. There he spent the next eleven years. Johann Peter Salomon, the great friend and patron of Haydn— who had formerly played with Franz Anton Ries in the court orchestra at Bonn—included Ries regularly in his Philharmonic concert series,[b] where a review praised his "romantic wildness".

During these London years he never lost touch with Beethoven and had a role in the London publications of many works of Beethoven after the peace of 1815, including the 1822 commission from the Philharmonic Society that resulted in the Choral Symphony.

In 1824 Ries retired to Germany with his English wife, Harriet Mangeon, but returned to musical life in Frankfurt am Main as composer and conductor. In 1834 he was appointed head of the city orchestra and Singakademie in Aachen, for whom he wrote two oratorios, Der Sieg des Glaubens (1829) and Die Könige in Israel (1837), both of which have been recorded. In addition, he was festival director of the Lower Rhenish Music Festival eight times - between 1824 and 1837. He died at Frankfurt am Main, aged 53.

Cecil Hill wrote a scholarly thematic catalog, listed below, of this composer's works: for each work he provided incipits (opening themes) for each movement, dedications, known early reviews, and known dates of composition.

While one of the few widely circulated recordings of Ries's music was for some time that of his third piano concerto, all of his symphonies, the other concertos, and a number of chamber works are now available on compact disc and his surviving music for piano and orchestra and chamber works are the focus of ongoing projects on various record labels as well.