RI
- RI – (s) Rex et Imperator, Regina et Imperatrix King-Emperor
- RI – (s) Rhode Island (postal symbol)
- RIAA – (i) Recording Industry Association of America
- RIBA – (a) Royal Institute of British Architects
- RIF
- (i) Reduction In Force (layoffs)
- Resistance Index for Frostbite
- Reading Is Fundamental
- RILA – (a) Retail Industry Leaders Association
- RIMVS – (i) Retinal Imaging Machine Vision System
- RINO – (a) Republican In Name Only
- RIP
- (a/i) Relief In Place
- (i) requiescat in pace (Latin for "may he/she/they rest in peace")
- RIS
- (i) Range Instrumentation System
- Réseau Info Sports (French, roughly "Sports News Network" — Canadian French-language TV channel)
- RISC – (i) Reduced Instruction Set Computer
- RISD – (p) Rhode Island School of Design ("riz-dee")
- RISTA – (a) Reconnaissance, Intelligence, Surveillance, and Target Acquisition (see also ISTAR)
- RWH – (a) Rain Water Harvesting
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