Wind shear is a collective term for sudden, brief and highly localised changes in wind direction and speed.

Aircraft are most at risk from wind shear during landing. When encountered close to a runway at low altitude, it may cause pilots to abandon their approach or landing. To help identify it in good time, modern commercial airliners are fitted with an enhanced ground proximity warning system (EGPWS). Air traffic controllers also warn arriving and departing aircraft of recent incidents of wind shear reported by pilots.