Basis is a set of middleware programs and tools from SAP, the German company whose comprehensive R/3 product is used to help manage large corporations. SAP provides the underlying base (thus the name) that enables applications (such as FI, CO, and SD, for example) to be interoperable and portable across operating systems and database products.

R/3 Basis includes client/server architecture and configuration, a relational database management system (RDBMS), and a graphical user interface (GUI). In addition to the interface between system elements, Basis components include a development environment for R/3 applications, and a data dictionary, as well as user and system administration and monitoring tools.