EDMX is an extension characteristic of files used to save data models by a software tool called ADO.NET. This software is part of the Microsoft Visual Studio development environment. The EDMX file stores the database skeleton. This information concerns, inter alia, database tables with their fields and types or relations between tables.

Such database schemes are created on the basis of the Entity Data Model (EDM), which is an extension of the Entity-Relationship model. These schemas are supported by SQL Server.