Encyclopedias, Almanacs, Transcripts, and Maps
- Theodor Ambrose Hubert Schwann
- Theodor Boveri
- Theodor Escherich
- Theodor Ludwig Wilhelm von Bischoff
- Theodor Svedberg
- Theodor Zwinger
- Theodore Harold Maiman
- Theodore Roosevelt
- Theodoric of Freiberg
- Theodoric of Freiberg and Kamal al-Din al-Farisi Independently Formulate the Correct Qualitative Description of the Rainbow
- Theodoric, Bishop of Cervia
- Theodoros of Samos
- Theodorus of Cyrene
- Theodosius Grigor'evich Dobzhansky
- Theodosius of Bithynia
- Theologus
- Theomancy
- Theon of Alexandria
- Theon of Alexandria
- Theon, M(ax) (1850-1927)