Ignaz or Ignace Vitzthumb (also Witzthumb; 14 September 1724 – 23 March 1816) was an Austrian musician, composer and conductor active in the Austrian Netherlands. He was also music director of the La Monnaie theatre in Brussels.
Vitzthumb was born in Baden bei Wien. Arriving in Brussels in 1735 at the age of 11, he entered the service of archduchess Maria Elisabeth of Austria as a child-singer in her choir. Taught by Jean-Joseph Fiocco, then choirmaster of the Brussels chapel royal, Vitzthumb became a court drummer at sixteen, a post he held for more than 40 years alongside other roles. His half-brother, François-Antoine Vitzthumb, was a trumpeter in the court and his son Paul Vitzthumb (1761–1838) succeeded him as court drummer. After the War of the Austrian Succession, in which he had served in a regiment of Hungarian hussars, he returned to Brussels and took part in several chambers of rhetoric and compagnies bourgeoises, of which there were Francophone as well as Flemish versions. He showed off his talents as a violinist, conductor and theatre director, and was a member of the Concert bourgeois. He is also mentioned among the court musicians as a composer, tenor and violinist in 1758 and 1759, and as a composer from 1760 to 1775.
From 1761, he entered the Théâtre de la Monnaie as its composer and music master, and taught singing to young actors such as Angélique D'Hannetaire and Alexandre Bultos. In 1772, he and the singer Louis Compain became co-directors of the Théâtre, then Vitzthumb was sole director from 1774 to 1777. This period is considered to be one of the most fertile in the Théâtre de la Monnaie's life, and travellers like Charles Burney did not hesitate to praise the quality of the members of its acting troop and orchestra. Even so, the theatre soon went bankrupt and so Vitzthumb was forced to abandon his role as director, though he retained that of conductor.