Ludvig Harald Knudsen (18 August 1843 – 16 March 1924) was a Historicist Danish architect.

He was the son of Jens Christian Knudsen (1801-1856) and Johanne F. Jakobsen (1811-1866).

He apprenticed as a carpenter and was then admitted to the Royal Danish Academy of Fine Arts in 1860 where he studied under Gustav Friedrich Hetsch.

After his graduation in 1869, he worked for both Christian Hansen and Ferdinand Meldahl.

Knudsen died in Copenhagen and was buried at Vestre Kirkegård.