Costco Wholesale Corporation is the largest American membership-only warehouse club. In 2015, Costco was the second largest retailer in the world after Walmart.

Costco focuses on selling products at low prices, often at very high volume. These goods are usually bulk-packaged and marketed primarily to large families and businesses.

Costco typically carries a limited number of brands or varieties where the item is essentially the same. This results in a high volume of sales for each vendor, allowing further reductions in price, and reducing marketing costs. A typical Costco warehouse carries only 4,000 distinct products, while a typical Walmart Supercenter carries approximately 140,000 products.

Costco's private label products are branded with its Kirkland Signature label.