REJIS is a regional data processing center serving governmental agencies in the greater St. Louis, Missouri area. The acronym stands for REgional Justice Information Service. REJIS is a joint commission of the City and County of St. Louis. The Commission was created when the Mayor of the City of St. Louis and the County Executive for St. Louis County signed a Cooperative agreement. The Cooperative agreement was authorized by ordinances passed by the Board of Aldermen in St. Louis City and the County Council in St. Louis County. As the name implies, REJIS has focused on providing services to the criminal justice community, and as such is classified as a criminal justice agency. The charter, however does not restrict REJIS to serving criminal justice agencies.

On behalf of their client agencies REJIS also provides fee-based services to other governmental agencies and the private sector. Members of The Missouri Bar Association use a service called MoBar Net, members of the private security community may use a service called PS Net and other governmental agencies can use a service called GA Net.