| Acronym | Meaning |
| RTIL | Room-temperature Ionic Liquid |
| RTK | Receptor Tyrosine Kinase |
| RTKNET | Right-to-Know Network |
| RTM | Resin-transfer Molding |
| RTMS | Room Temperature Molten Salt |
| RTMS | Repetitive Transcranial Magnetic Stimulation |
| RTNS | Rotating Target Neutron Source |
| RTO | Rapid Thermal Oxidation |
| RTO | Regenerative Thermal Oxidizer |
| RTP | Research Triangle Park |
| RTP | Rapid Thermal Processing |
| RTP | Reinforced Thermoplastic |
| RTP | Room Temperature Phosphorescence |
| RTPCR | Reverse Transcriptase Polymerase Chain Reaction |
| RTPM | Radical Triplet Pair Mechanism |
| RTPM | Real-time Polarization Modulation |
| RTRP | Reinforced Thermosetting Resin Pipe |
| RTT | Resonant Tunneling Transistor |
| RTU | Remote Terminal Unit |
| RTV | Room Temperature Vulcanization |
| RUDAD | RUmen-Derived Anaerobic Digester |
| RUP | Rumen-undegradable Protein |
| RUP | Restricted Use Pesticide |
| RUS | Resonant Ultrasound Spectroscopy |
| RUSLE | Revised Universal Soil Loss Equation (erosion Model) |
| RUSTIC | Risk Of Unsaturated/saturated Transport And Transformation Of Chemical Concentrations |
| RVAAP | Resource Values Affected By Air Pollution |
| RVB | Resonating Valence Bond (theory Of High-tc Superconductors) |
| RVC | Reticulated Vitreous Carbon (electrode) |
| RVCM | Renormalized Virtual-crystal Method (for Electronic Structure) |
| RVCM | Residual Vinyl Chloride Monomer |
| RVD | Regulatory Volume Decrease |
| RVDT | Rotary Variable Differential Transformer |
| RVLM | Rostral Ventrolateral Medulla |
| RVP | Reid Vapor Pressure (used For Gasoline Volatility) |
| RVR | Renal Vascular Resistance |
| RVS-SCF | Reduced Variational Space-self-consistent Field (in Quantum Calcns. On Hydrogen Bonding) |
| RW | Retonation Wave [backwardly Propagated Detonation Wave] |
| RWA | Rotating Wave Approximation |
| RWKB | Relativistic Wentzel-Kramers-Brillouin |
| RWMC | Radioactive Waste Management Complex (INEL) |
| RXES | Resonant X-ray Emission Spectra |
| RXF | Refracted X-ray Fluorescence |
| RXR | Retinoid X Receptor |
| RXTE | Rossi X-ray Timing Explorer |
| RYDMR | Reaction Yield Detected Magnetic Resonance |
| RZM | Root Zone Method (of Wastewater Treatment) |
| RZWQM | Root Zone Water Quality Model |
| S-MPPT | Supermolecular Moeller-Plesset Perturbation Theory |
| S/MTD | STOL Maneuvering Technology Demonstrator (program) |