Isidore (or Julien) Bertheaume (ca. 1752 – 20 March 1802) was a French classical composer and violinist.
Born in Paris, Bertheaume was a child prodigy. He was the nephew of violinist Jacques Lemière the eldest (who died in 1771). According to the Mercure de France of April 1761, at the age of nine and a half, he obtained great success at the Concert Spirituel with a sonata by Lemière and another by
Felice Giardini. In 1767, he joined the Orchestra of the Paris Opera and became its first violin in 1774. Then in 1788, he was appointed concertmaster of the Opéra-Comique orchestra. Between 1788 and 1791, he conducted the orchestra of the Concert Spirituel. In 1791 Bertheaume left France and held several posts in northern Germany until 1801. Via Copenhagen and Stockholm he emigrated to Russia, where he became first violin in the tsar's court orchestra. He died a few months after arriving at St-Petersburg.
