An online Reverse Auction (RA) is an internet-based (electronic commerce) acquisition tool that allows the government to procure goods and services from suppliers in a competitive environment in which sellers, anonymously, bid prices down until the auction is complete.

A reverse auction is simply the opposite of a traditional auction. In a traditional auction, the seller offers an item for sale and multiple potential buyers submit sequentially higher bids for the item. Conversely, in a reverse auction, there are multiple sellers of items that compete for the business of a single buyer. During this competition the sellers ultimately drive the price of the item down.