SAP
Amazon.com began using the SAP software suite in 2008 after the company came to the conclusion it could not meet its long-term goals with the systems it was then using.
Amazon has implemented a number of modules in their business suite implementation (order management, financials, HR, purchasing, and receiving/inventory control).
Read and learn more about SAP ERP software here.
You can see which software is used by other wholesale & distribution companies and retailers here.
Did you know that Apple also uses SAP?