| rlib | Rust Compiled Library |
| rll | Microsoft Resource Library |
| rln | Alpha Four Field Rules |
| rlz | CA-Realizer Source Code |
| rmd | R Markdown Source Code |
| rmk | Clipper RMake File |
| rms | Retek Merchandising System Settings |
| rmuf | Alpha Five Runtime Users Data |
| rnc | RELAX NG Compact Syntax |
| rng | RELAX NG Syntax File |
| rnw | Sweave Document |
| robo | RoboMind Source Code |
| rodl | RemObjects Definition Language |
| ron | Ron Document |
| rotest | RemObjects SDK Test Data |
| rotestresult | RemObjects SDK Test Results Data |
| rpd | RapidPLUS Application File |
| rpf | ProWorx NXT Cross-reference Pointer |
| rplib | Axure RP Widget Library |
| rpo | GCC Compiler Template Object |
| rpp | RPP Script |
| rpp | SymbianOS Pre-processed Resource |
| rpp | FactoryTalk View Studio RecipePlus Component File |
| rpy | RenPy Script |
| rpyb | RenPy Bytecode |
| rpyc | RenPy Compiled Script |
| rpym | RenPy Module |
| rpymc | RenPy Module |
| rqc | Micro Focus Revolve Compiled Script |
| rqs | Micro Focus Revolve Script |
| rrc | BlackBerry Resource Content |
| rrh | BlackBerry Resource Header |
| rsc | Pegasus Mail Compiled Resource |
| rsg | SymbianOS Resource Header |
| rsi | Reactis Info File |