Louis Étienne Joseph Marie de La Vallée-Poussin (1 January 1869 – 18 February 1938) was a Belgian Indologist and scholar of Buddhist Studies.

He studied Sanskrit, Pali, and Avestan under Charles de Harlez and Philippe Colinet from 1888 to 1890 at the University of Louvain, receiving a docteur en langues orientales in July 1891.

Moving to Paris, he began his studies at the Sorbonne that same year under Victor Henri and Sylvain Lévi.

In 1893, he attained a professorship at the University of Ghent teaching comparative grammar of Greek and Latin, a position which he held until his retirement in 1929.

Louis de La Vallée-Poussin died on February 18, 1938, in Brussels, Belgium at the age of 69.