Encyclopedias, Almanacs, Transcripts, and Maps
- Siegel, Jerome (“Jerry”)
- Sierra (Ecuador)
- Sierra (Peru)
- Sierra Méndez, Justo (1848–1912)
- Sierra O'Reilly, Justo (1814–1861)
- Sierra, Stella (1917–1997)
- Siete de Marzo
- Siete Partidas
- Sigaud, Eugenio de Proença (1889–1979)
- Siger of Brabant (c. 1240–c. 1281/1284)
- Sigüenza y Góngora, Carlos de (1645–1700)
- Sigwart, Christoph (1830–1904)
- Sikhs
- SILENT LETTER
- Siles Zuazo, Hernán (1914–1996)
- Silesians
- Siletz
- Silk Industry and Trade
- Silva Henríquez, Raúl (1907–1999)
- Silva Herzog, Jesús (1892–1985)