"The Dragon" is a short story by American writer Ray Bradbury, originally published in 1948 in the magazine Esquire. A limited edition (352 copies, signed and numbered or lettered) of the story was published by Footsteps Press in 1988.
It appears in A Medicine for Melancholy (1959), R is for Rocket (1962), Classic Stories 1 (1990), and Bradbury Stories (2003).
Plot
The story concerns two knights who have a mission to slay a dragon. They describe the dragon as huge, fire-breathing, and horrific, having only one eye. They charge the dragon but fail, presumably dying in the attempt.
The "dragon" is then revealed to be a steam train, and its single eye is the train's headlight. The operators discuss the encounter but continue on without attempting to find the knights.
Sources
Chalker, Jack L.; Mark Owings (1998). The Science-Fantasy Publishers: A Bibliographic History, 1923-1998. Westminster, MD and Baltimore: Mirage Press, Ltd. p. 264.