Windage is a force created on an object by friction when there is relative movement between air and the object.

There are two possible causes of windage:

1. the object is moving and being slowed by resistance from the air
2. a wind is blowing producing a force on the object

The term can refer to :

• either, the effect of the force, for example the deflection of a missile or an aircraft by a cross wind
• or, the area and shape of the object that make it susceptible to friction, for example those parts of a boat that are exposed to the wind.

Aerodynamic streamlining can be used to reduce windage.

There is a similar hydrodynamic effect to windage.