Ascaridia galli is a parasitic roundworm belonging to the phylum Nematoda. Nematodes of the genus Ascaridia are essentially intestinal parasites of birds. A. galli is the most prevalent and pathogenic species, especially in domestic fowl, Gallus domesticus Linnaeus, 1758. It causes ascaridiasis, a disease of poultry due to heavy worm infection, particularly in chicken and turkeys. It inhabits the small intestine, and can be occasionally seen in commercial eggs.