A weather vane (or weathercock) is an instrument for showing the direction of the wind . They are typically used as an architectural ornament to the highest point of a building.

Although partly functional, weather vanes are generally decorative, often featuring the traditional cockerel design with letters indicating the points of the compass. Other common motifs include ships, arrows and horses. Not all weather vanes have pointers.

The word 'vane' comes from the Old English word 'fane' meaning 'flag'.