Shigella boydii is a Gram-negative bacterium of the genus Shigella. Like other members of the genus, S. boydii is a nonmotile, nonsporeforming, rod-shaped bacterium which can cause dysentery in humans through fecal-oral contamination. S. boydii is the most genetically divergent species of the Shigella genus. There are 19 known serotypes of Shigella boydii. S. boydii is restricted to the Indian subcontinent. The species is named after the American bacteriologist Mark Frederick Boyd.