A tandem wing is a wing configuration in which a flying craft or animal has two or more sets of wings set one behind another. All the wings contribute to lift.
The tandem wing is distinct from the biplane in which the wings are stacked one above another, or from the canard or "tail-first" configuration where the forward surface is much smaller and does not contribute significantly to the overall lift.
In aviation, tandem wings have long been experimented with, but few designs have ever been put into production.
Tandem wings in nature occur only in insects and flying fish, although in the past there have been tandem-wing flying reptiles.