"To Build a Fire" is a short story by American author Jack London. There are two versions of this story. The first one was published in 1902, and the other was published in 1908. The story written in 1908 has become an often anthologized classic, while the 1902 story is less well known.

The 1908 version is about an unnamed male protagonist who ventures out in the subzero boreal forest of the Yukon Territory. He is followed by a native dog and is en route to visit his friends—ignoring warnings from an older man from Sulphur Creek about the dangers of hiking alone in extreme cold. The protagonist underestimates the harsh conditions and freezes to death after his fire is doused and he is unable to re-light it.

In the 1902 version, though the structure and storyline are similar, the weather is not as cold and horrendous, no dog follows the protagonist, the fire is not doused, and the man (named Tom Vincent in this version) suffers only from severe frostbite and survives to become a more melancholic but wiser person.

"To Build a Fire" is an oft-cited example of the naturalist movement that portrays the conflict of man versus nature. It also reflects London's personal experiences in the Yukon Territory.