Land Niedersachsen

Castor most commonly refers to:

Castor (star), a star in the Gemini constellation
Castor, one of the Dioscuri/Gemini twins Castor and Pollux in Greco-Roman mythology

Castor or CASTOR may also refer to:

Science and technology

Castor (rocket stage), a family of solid-fuel rocket stages
Castor (software), data binding framework for Java
CASTOR (nuclear waste), cask for storage and transport of radioactive material
CASTOR experiment, "Centauro and Strange Object Research" at CERN
CASTOR (spacecraft), proposed space telescope
Castor sugar, fine sugar
Caster (or Castor), an undriven wheel
Caster (or Castor) angle, relevant to a steered wheel

Castor oil plant, plant from which castor bean grows
- Castor oil, oil of the castor bean
- Castor wax, produced from castor oil
Castor, a genus name of the beaver
- Castoreum, natural scent derived from the beaver

Castor of Rhodes, Greek grammarian and rhetorician
Drusus the Younger (13 BC – 23 CE), Roman consul, son of the Emperor Tiberius, nicknamed "Castor"
Antonius Castor, ancient botanist
Saint Castor, the name of several Christian saints
- Castor of Apt (died c. 420), French bishop of Apt
- Castor of Karden (died c. 400), German priest and hermit

Castor Oyl, fictional character in the Popeye cartoons
Castor Troy, fictional character in the 1997 movie Face/Off, portrayed by Nicolas Cage and John Travolta
Castor, fictional character in the video game Spartan: Total Warrior
Lord Castor, fictional character in the 2007 movie The Harpy
Castor, fictional character in Tron: Legacy, portrayed by Michael Sheen
"Castor, Gobernador" fictional character in The Courts of the Morning by John Buchan
"Castor Wilds" fictional location in The Legend of Zelda: The Minish Cap by Nintendo
"Castor", fictional persona in the video game Persona 3. Castor is used by one of the playable characters, Shinjiro Aragaki

Castor, Alberta, Canada
Queue de Castor River, Eeyou Istchee Baie-James, Jamésie, Nord-du-Québec, Canada
Rivière aux Castors Noirs, river in Quebec, Canada
Castor River (Ontario), Ontario, Canada
Castor, Louisiana, Louisiana, United States
Castor Creek, Louisiana, United States
Castor River (Missouri), United-States
Castor (mountain), in the Pennine Alps on the border between Switzerland and Italy
Castor Bay, Auckland, New Zealand
Castor, Cambridgeshire, England
Castor Temple, a summit in the Grand Canyon, United States
Castor, an old name for Caistor St. Edmund, Norfolk, England
Castor (crater) on Saturn's small moon Janus

Castor (band), American rock band
Castor (cloth), a woollen fabric
Castor (trucks), a brand used by Swedish truck manufacturers Tidaholm in the 1910s
Castor Cracking Group, Swedish music group
HMS Castor, the name of more than one ship of the British Royal Navy
Castor (1782 ship), a vessel launched in 1782 that made one voyage to Bengal for the British East India Company and that was last listed in 1808.
Castor gloves, gloves made from the skin of lambs or deer
Castor hat
Project Castor, a set of male clones in the TV series Orphan Black
Castore (brand), British sportswear and athletic clothing company