RATP may refer to:
Transportation:
- RATP Group, or Régie Autonome des Transports Parisiens, a public transport operator based in Paris, France
- RATP Iași (Regia Autonomă de Transport Public Iași), a transit operator responsible for public transportation in Iași, Romania
- RATP Ploiești (Regia Autonomă de Transport Public Ploiești), a transit operator responsible for public transportation in Ploiești, Romania
Computation:
- Reliable Asynchronous Transfer Protocol (RATP), defined in RFC 916