Martingale (probability theory), a stochastic process in which the conditional expectation of the next value, given the current and preceding values, is the current valueMartingale (tack) for horsesMartingale (collar) for dogs and other animalsMartingale (betting system)Martingale (rigging)In the sport of fencing, a martingale is a strap attached to the sword handle to prevent a sword from being dropped if disarmed.In the theatrical lighting industry, a Martingale is an obsolete term for a twofer, or occasionally a threefer.

The concept of martingale in probability theory was introduced by Paul Pierre Lévy, and much of the original development of the theory was done by Joseph Leo Doob. Part of the motivation for that work was to show the impossibility of successful betting strategies.