Auctions are a common method for people to contest for a variety of goods, such as electronics, properties, and artwork, where the highest bid is selected. However, issues such as: non-delivery, misinterpretation, shill bidding, and the sale of black market goods have deterred users from participating in online auctions. This research focused on designing and developing an online auction system to effectively address the issue of shill bidding- a type of fraud where a seller or third party artificially inflates the price of an item by submitting false bids. The system was developed using HTML, CSS, and JavaScript for the front end, and PHP and MySQL for the back end. Several features were incorporated to prevent shill bidding, including the use of SKU codes known only to the system administrator, the elimination of a search bar, and the introduction of user profiles and seller accounts. The software was tested to evaluate its effectiveness in mitigating shill bidding. The results showed a significant decrease in suspicious bids and an increase in user satisfaction indicating that the system is a valuable tool for preventing shill bidding in online auctions.