Leadlights or leaded lights are decorative windows made of small sections of glass supported in lead cames. The technique of creating windows using glass and lead came is discussed at lead came and copper foil glasswork. The term leadlight could be used to describe all windows in which the glass is supported by lead but traditionally, a distinction is made between stained glass windows and leadlights, the former being associated with the ornate windows of churches and other such works of architecture and the latter with the windows of vernacular commercial and domestic architecture and defined by its simplicity.

Since the traditional technique of setting glass into lead cames is the same in both cases, in the late 20th century the divisions between "leadlight" and "stained glass" became blurred, and the terms are now often used interchangeably for any window employing this technique, while the term "stained glass" is often extended in application to any windows, sculpture, and works of art using coloured glass.