RTA or Rta, is a three letter acronym that could refer to:
Traffic or transit authorities
- Regional Transportation Authority (Illinois), serving Chicago, United States
- Regional Transportation Authority (Tennessee), serving Nashville, United States
- Greater Cleveland Regional Transit Authority, Ohio, United States
- Greater Dayton Regional Transit Authority, Ohio, United States
- Roads and Transport Authority, serving Dubai, UAE
- Roads and Traffic Authority in New South Wales, Australia
- Riverside Transit Agency in Riverside County, California, United States
- New Orleans Regional Transit Authority, United States
- Central Puget Sound Regional Transit Authority, United States
- South Florida Regional Transportation Authority, United States
- One of 15 Regional Transit Authorities in Massachusetts#Transportation
Science and technology
- Real Time Analyzer for audio applications, such as analyzing sound
- the retrolateral tibial apophysis of spiders
- Renal tubular acidosis
- Road traffic accident, see Road traffic collision