A mountain-gap wind, gap wind or gap flow is a local wind blowing through a gap between mountains.

The phenomenon of Mountain-gap wind or squamish or outflow affects the fjords of Canada and Norway.

If such events accelerate through mountain passes, dangerously accelerated mountain-gap winds can result, such as the Tehuantepecer and Santa Ana winds.

Tehuantepecer, or Tehuano wind, is a violent mountain-gap wind traveling through Chivela Pass, most common between October and February, with a summer maximum in July.