Karl Henrik Ludolf Nielsen (29 January 1876 – 16 October 1939) was a Danish composer, violinist, conductor, and pianist.
Today he is considered one of the most important Danish composers of the early 1900s (together with the more famous Carl Nielsen).
When about 20, Nielsen started composing, at the same time as Tivoli Orchestra hired him as a violinist.
Some of his works were performed in 1899, but his first major success was with the symphonic poem Regnar Lodbrog, which gained him an additional scholarship that gave him the opportunity to spend time in the musically rich city of Leipzig, where he composed a few string quartets and had them published.
The two most important works from this period are his ballet Lackschmi (1922) and the orchestral suite Skovvandring (Forest Journey), along with almost 100 Lieder.