- r ... Rabbit Hole
- Rabbit Hole ... Racette, Patricia Lynn
- Rach Gia ... Radcliffe College
- Radcliffe Institute for Advanced Study at Harvard University ... radiation, gravitational
- radiation-damage dating ... radio reflector
- radio relay ... radius of convergence
- radius of gyration ... Rafsanjani, Ali Akbar Hashemi
- Rafsanjani, Hashemi ... Rahit
- rahit-nama ... rain forest
- rain frog ... Raise the Roof
- raised bog ... Rajbansi
- Rajbari ... Rallus aquaticus
- Rallus limicola ... Ramakrishnan, Venki
- Ramakrishnan, Venki ... Rameses VI
- Rameses VII ... Ramos, Mel
- Ramos, Samuel ... Rana family
- Rana Kao ... random walk
- random-access memory ... Ranke, Leopold von
- Rankeanism ... Rape of Persephone, The
- Rape of Proserpine, The ... Rare Beauty
- Rare but Not Forgotten ... Raso Island
- Rasofsky, Barnet David ... Ratdolt, Erhard
- rate constant ... ratooning
- Ratramnus ... Raven, Bertram
- Raven, Simon ... ray tracing
- Ray, Aldo ... Razmārā, ʿAlī
- Ražnatović, Željko ... reaction formation
- reaction injection molding ... Reagan, Nancy Davis
- Reagan, Ron ... reality principle
- Reality Sandwiches ... reboil
- rebolera ... reciprocity
- Reciprocity Treaty ... Recopilación subtilissima
- record ... Recurvirostra americana
- Recurvirostra andina ... red crossbill
- red crowberry ... Red Mountain Formation
- Red Mountain Republicans ... Red Star
- Red Star Belgrade ... red-winged tinamou
- reda ... Redon, Odilon
- Redonda ... reed organ
- reed pen ... referee
- reference ... Reform Judaism, Union for
- Reform Movement ... Regan, Donald
- Regan, Tom ... Región Occidental
- Region of the Rapids ... Regula secunda
- Regulae ad Directionem Ingenii ... Reicha, Anton
- Reichardt, Kelly ... Reincarnation of Rama, The
- reindeer ... Reiwa period
- Reiyū-kai ... relaxed walk
- relaxin ... religious doctrine
- religious drama ... Remedia amoris
- remedial education ... Renaissance Scholasticism
- Renaissance Theatre Company ... René I
- René Magritte Museum ... renvoi
- Renwick Gallery ... reportage
- Reporters sans Frontières ... Republic of Mauritius
- Republic of Palau ... Requiem
- Requiem Canticles ... Reserve Bank of Australia
- Reserve Bank of India ... Resistência Nacional Moçambicana
- Resistible Rise of Arturo Ui, The ... respiratory-chain phosphorylation
- resplendent quetzal ... resultant
- resultant ... retinaculum
- retinal ... Return of the Soldier, The
- Return of the Soldier, The ... revendication
- Revenge ... Revised Standard Version
- Revised Statutes of the United States ... Revue de Paris
- Revue de synthèse historique ... Rezzonico, Carlo della Torre
- reʾem ... Rhäticus, Georg Joachim
- Rhätikon Mountains ... Rhine wine
- Rhine, Confederation of the ... Rhizomys sinensis
- Rhizomys sumatrensis ... Rhododendron tomentosum
- Rhododendron yedoense ... Rhynchospora
- Rhynchotrema ... ribbon plant
- ribbon reef ... rice rat
- rice starch ... Richard le Bon
- Richard le Grant ... Richelet, César-Pierre
- Richelieu River ... rickardite
- Rickenbacker, Eddie ... Rider on the White Horse, The
- Rider University ... Rifai, Samir al-
- rifampicin ... right to bear arms
- right to counsel ... Rijsbrack, Jan Michiel
- rijsttafel ... rimu
- rímur ... Ringley, Jennifer
- Ringling Bros. and Barnum & Bailey Circus ... Río Huallaga
- Rio Jacuí ... Ripcord
- ripeness doctrine ... Rising
- rising expectations ... Rittenhouse, David
- Ritter ... River Thieves
- River War, The ... Riyāḍ, Maḥmūd
- Riyāḍ, Muḥammad ʿAbd al-Munʿim ... Road Not Taken, The
- road octane number ... Robbia, Giovanni della
- Robbia, Girolamo Della ... Robert Wood Johnson Foundation
- Robert’s Rules of Order ... Robertson, Robbie
- Robertson, Roland ... Robinson, John
- Robinson, John ... Roccella tinctorum
- Rocco, San ... rock cress
- Rock criticism ... Rockefeller
- Rockefeller Center ... Rocky II
- Rocky III ... Rodna
- Rodna Massif ... Roerich, Nicholas
- Roermond ... Rohan, Charles de, prince de Soubise
- Rohan, Château des ... Rold Forest
- Roldán, Francisco ... Rolls of Oleron
- Rolls, Charles Stewart ... Roman numeral
- Roman numeral converter ... Romano, Girolamo di
- Romano, Giulio ... Romeo i Dzhulyetta
- Romeo, Nicola ... Roncevaux Pass
- Ronchi, Vasco ... room-and-pillar mining
- room-temperature-vulcanizing silicone rubber ... ropefish
- Roper River ... Roscius
- Roscius, The Young ... Rosebery
- Rosebery, Archibald Philip Primrose, 5th earl of ... Rosetta
- Rosetta ... Ross, Steve
- Ross, Wilbur ... Rostropovich, Mstislav
- Rostropovich, Mstislav Leopoldovich ... Roter Sand Lighthouse
- roth cleas ... rotte
- rotten borough ... Round Mound of Rebound
- Round Mountain ... Rovaniemi
- rove beetle ... Roy Mata
- Roy Rogers and Dale Evans Show, The ... Royal Dublin Society
- Royal Dutch Airlines ... Royal Portal
- Royal Postal System ... RPP
- RPP cycle ... rubbish disposal system
- rubble ... Ruby, Jack
- Ruby, Jack L. ... Rudolph, Alan
- Rudolph, Eric ... Ruggie, John Gerard
- Ruggieri, Michele ... Rule, Jane
- Rule, Jane Vance ... Rumors
- Rumors of War ... running of the bulls
- Running on Empty ... Rurales
- Rurik ... Russell, Eric Frank
- Russell, Ernestine Jane Geraldine ... Russian olive
- Russian Orthodox Church ... Rutaceae
- Rutan, Burt ... Ruwenzori National Park
- Ruwenzori otter shrew ... Rydberg, Viktor
- Ryde ... Rzhev
