A database is a collection of related data, organized to allow a computer to efficiently answer questions about that data. A database management system (DBMS) is the software used to store, manage, and retrieve the data in a database. There are several different types of DBMS, the most important of which is the relational DBMS, which stores data as a set of carefully structured tables. However, the conventional relational DBMS alone is not sufficient for storing geospatial data. This entry begins with an overview of DBMS features and then outlines the common types of DBMS. It concludes with a more in-depth examination of the most popular type, relational DBMS, and discusses how these systems are implemented in GIS.