A bug tracking system or defect tracking system is a software application that keeps track of reported software bugs in software development projects. It may be regarded as a type of issue tracking system.

Many bug tracking systems, such as those used by most open-source software projects, allow end-users to enter bug reports directly. Other systems are used only internally in a company or organization doing software development. Typically bug tracking systems are integrated with other project management software.

A bug tracking system is usually a necessary component of a professional software development infrastructure, and consistent use of a bug or issue tracking system is considered one of the "hallmarks of a good software team".