Fly-by-Night is a children's novel by K. M. Peyton originally published by Oxford University Press in October 1968.

It is about an 11-year-old girl, Ruth Hollis, who buys a pony called Fly for £40 from a dealer.

She expands his name to Fly-by-Night and attempts to train him herself without much success.

A rivalry develops between Ruth and another girl, Pearl, who owns a pedigree Arabian mare named Milky Way.

Fidra Books is currently publishing Fly-By-Night, with the sequel, The Team, expected in the future.