The Big Time is a science fiction novel by Fritz Leiber published in 1958. It was awarded the Hugo Award during 1958.

The Big Time is a story involving only a few characters, but with a vast, cosmic back story.

The storyline features members of one of two factions, both capable of time travel, engaged in a long-term conflict called 'The Change War'. Their method of battle involves changing the outcomes of events throughout history (temporal war). The two opposing groups are nicknamed the Spiders and the Snakes after their respective sponsors. The true forms or identities of the Spiders and the Snakes, how those nicknames were chosen, or whether they are in any way descriptive are all unknown.

'You can't know there's a war on-for the Snakes coil and Spiders weave to keep you from knowing it's being fought over your live and dead body!'

Algis Budrys praised The Big Time as evidence that Leiber was the only science fiction writer of his generation 'who as a matter of course and conviction saw through the mores and circumstances which are now proving nonviable not only in commercial literature but in what we can call life as well.'

In 2012, it was selected for inclusion in the Library of America's two-volume compilation American Science Fiction: Nine Classic Novels of the 1950s.

The Big Time was published originally in two parts in Galaxy Magazine's March and April 1958 issues. It has many subsequent reprints in book form.