Nicolas Andry de Bois-Regard (1658 – 13 May 1742) was a French physician and writer. He played a significant role in the early history of both parasitology and orthopedics, the name for which is taken from Andry's book Orthopédie.
Andry was born in Lyon, and spent his early life preparing for the priesthood. His early studies were widespread, however, and he published a book on the usage of the French language in 1692. In his 30s he studied medicine at Reims and Paris, receiving his degree in 1697, and in 1701 he was appointed to the faculty of the Collège de France and the editorial board of the Journal des savants.
Andry's early medical work lies within the nascent germ theory of disease. His first book, De la génération des vers dans les corps de l'homme, was published in 1700, and translated into English in 1701 as An Account of the Breeding of Worms in Human Bodies. The book was an account of Andry's experiments with the microscope, building on the earlier work of Antonie van Leeuwenhoek, whom Andry cites frequently. Unlike Leeuwenhoek, Andry's purpose is specifically medical, and his experiments with the microscope led him to believe that the microorganisms he called "worms" were responsible for smallpox and other diseases.
The book contains a detailed discussion of spermatozoa, which Andry calls "spermatic worms." He observes: "If you cut up a dog, and after you have taken off one Testicle, by the help of a Microscope examine the Humour that comes out of the deferent vessel, you shall discover in it such a hideous number of little worms, that you shall hardly be able to believe your own Eyes." Andry confirms an argument previously made by Leeuwenhoek, that spermatozoa are "the occasion of the Generation of all Animals." Though Andry recognizes the importance of sperm to reproduction, however, he addresses their workings primarily in the context of parasitology, and essentially considers spermatozoa to be a unique species of parasitic worm.