采光是指为调整建筑物室内环境，而从室外引入自然光。与通风都是维持室内环境卫生舒适的必要行为，是建筑装设窗户的重要目的之一。另外，在人工照明发达的现代，采光也包含了节约能源的目的。除了设窗户之外，采光还可以用反射镜面、光纤、反射板、导光板等手段达成，让光甚至能到达建筑物深处。各国的建筑法规内常会包含采光的相关规定。

Daylighting is the practice of placing windows or other openings and reflective surfaces so that during the day natural light provides effective internal lighting. Particular attention is given to daylighting while designing a building when the aim is to maximize visual comfort or to reduce energy use. Energy savings can be achieved from the reduced use of artificial (electric) lighting or from passive solar heating. Artificial lighting energy use can be reduced by simply installing fewer electric lights because daylight is present, or by dimming/switching electric lights automatically in response to the presence of daylight, a process known as daylight harvesting.