Open e-PRIOR is an open-source e-procurement platform that allows practical implementation of interoperable electronic services within any public administration.

It plays the role of intermediary between the back-office applications of the public administration and the Pan-European Public Procurement OnLine (PEPPOL) interoperability initiative. It has been designed to interoperate with a large number of applications of heterogeneous nature. The platform is connected to PEPPOL via its own Access Point, facilitating the cross-border exchange of e-procurement documents between, for example, a public administration in country A with suppliers in country B.

The platform has been developed under the ISA (Interoperability Solutions for European Public Administrations) programme, by the Directorate-General for Informatics (DIGIT) of the European Commission and it was deployed within DIGIT in 2009. Other Directorate-Generals, European Agencies and Institutions are implementing the system and it is freely available to all Members States wishing to exchange standardised electronic procurement documents via secured communication channels.

The interfaces of Open e-PRIOR are based on the Business Profiles defined by CEN's workshop on Business Interoperability Interfaces for Public Procurement in Europe (CEN/ISSS WS/BII).