Blue John may refer to:
- Derbyshire Blue John, a form of fluorite mined in Derbyshire, England
- Blue John Cavern, a cavern in Castleton, Derbyshire where fluorite is mined
- Blue John Canyon, a canyon in Utah, United States, site of the Aron Ralston accident
- Blue John (album), an album by organist John Patton
- Lance-Constable Bluejohn, a character in the Discworld series, a member of Ankh-Morpork City Watch
- Blue John Gap, a fictional location in Arthur Conan Doyle's short story "The Terror of Blue John Gap"
Famous quotes containing the word blue:
“Buz, quoth the blue fly,
Hum, quoth the bee,
Buz and hum they cry,
And so do we:
In his ear, in his nose, thus, do you see?
He ate the dormouse, else it was he.”
—Ben Jonson (1572–1637)