Encyclopedias, Almanacs, Transcripts, and Maps
- Roosevelt, Theodore (1858 – 1919) American Politician and Conservationist
- Rorquals (Balaenopteridae)
- Ross Dependency
- Roszak, Theodore (1933 – ) American Social Critic
- Rothschild, Meyer Amschel
- Rotifera (Rotifers)
- Round-the-World Weather
- roundworm
- Rousseau, Jean-Jacques
- Roy, Ram Mohan
- Roʾsh Ha-Shanah and Yom Kippur
- RSPCA
- Ṛta
- Rubik, Ernö
- Ruckleshaus, William Doyle (1934 – ) American Former Environmental Protection Agency Administrator
- rudd
- Rugby Union Six Nations Championship
- Rugby Union World Cup
- Rūmī, Jalāl al-Dīn
- Runoff