Sam and the Firefly is a children's book by P. D. Eastman. It was written in 1958.

Sam, an owl, awakens one night and looks for a playmate. However, since it is the middle of the night, all the creatures are asleep. Sam then comes across a series of flying lights, one of which hits Sam in the head. It is Gus, a firefly. Gus shows Sam the trick he can do, which is he can make glowing lines in midair using his light. Sam is amazed and decides to have fun by having Gus follow him directly as he flies. Sam flies in the shape of various words; Gus finds this fun and decides to do more on his own. However, he has mischief on his mind.

First, he causes several cars to crash at an intersection by displaying "Go left", "go right", "stop", and "go" above. Sam wants to talk to him about this behavior, that it is dangerous and bad; however, Gus abandons Sam as he thinks Sam doesn't know how to have fun. Gus then continues to cause mischief; he causes several airplanes to get crossed up by displaying random directions, he causes people to overflow into a movie theater by displaying "COME IN! FREE SHOW" above it, and he changes a sign from "Hot Dogs" to "COLD HOT DOGS", deterring the hot dog maker's customers. The hot dog maker immediately nets Gus and puts him a jar and into his pickup truck. Sam sees this and is determined to save him.

Gus regrets not listening to Sam's warnings about having too much fun. The aforementioned pickup truck stalls on a railroad crossing with a train coming. Sam arrives at the scene and breaks the jar containing Gus, freeing him. Now free, Gus displays "STOP" several times in large letters. The locomotive's engineer sees Gus' messages and the truck on the tracks. The engineer applies the brake and stops the train just in time. The hot dog maker and the engineer and brakeman all call Gus a hero, and Gus and Sam fly off into the night. As dawn arrives, they must go back to their homes to sleep, since they are nocturnal. However, Gus continues to visit Sam's tree home every night to play.