Disclosed are various embodiments for implementing inventory pooling for multiple merchants. A first inventory of an item held at a first fulfillment center on behalf of a first merchant is contributed to a common pool of inventory. A second inventory of the item held at a second fulfillment center on behalf of a second merchant is contributed to the common pool of inventory. Fulfillment of an order placed by a customer of the first merchant is initiated from the second inventory of the item that was contributed by the second merchant to the common pool of inventory.