Simon-Joseph-Alexandre-Clément Denis was a Belgian painter active primarily in Italy.
Denis first studied in his native city of Antwerp, with the landscape and animal painter H.-J. Antonissen. The work of Balthasar Paul Ommeganck also influenced his style.
He moved to Paris in the 1780s, and soon gained the patronage of genre painter and art dealer Jean-Baptiste-Pierre Lebrun [fr], whose support allowed him to move to Rome in 1786. His paintings there attracted favorable attention, and in 1787 he married a local woman. He remained close to the Flemish community in Rome, and in 1789 was elected to head the Foundation St.-Julien-des-Flamands. He also developed ties within the French artistic community; Élisabeth-Louise Vigée-Le Brun stayed with him for some days in 1789 and that same year he and she traveled with François-Guillaume Ménageot to visit Tivoli. François Marius Granet sought his advice when he arrived in Rome in 1802.
In 1803, he was elected to the Accademia di San Luca; in 1806 he settled for good in Naples, becoming court painter to Joseph Bonaparte. Denis died in 1813.