Sam's Club, operated by retail titan Walmart, serves as Costco's largest and most direct warehouse club competitor on a global scale, boasting comparable multi-billion-dollar revenues, massive membership bases, and sprawling warehouse networks across North America. BJ's Wholesale Club acts as another major domestic competitor, though its geographic presence is concentrated more heavily along the Eastern seaboard compared to the coast-to-coast footprints of Costco and Sam's Club.