Modular vending machines for storing and dispensing products to consumers. A modular vending machine may include a product storage system, a user interface, and a control unit. Several modular vending machines may be stacked and/or arranged together in various configurations. Several modular vending machines may be linked electronically and may communicate with each other and/or with a user mobile device over a network. A modular vending machine may automatically complete a transaction with the consumer, where the consumer removes a product from the modular vending machine. A consumer may access and purchase products from several modular vending machines in one transaction.