thumb|upright=1.3|South Solar of [[Bunratty Castle in County Clare, Ireland]]
The solar was a room in many English and French medieval manor houses, great houses and castles, mostly on an upper storey, designed as the family's private living and sleeping quarters. Within castles they are often called the "Lords' and Ladies' Chamber" or the "Great Chamber".
The solar was generally smaller than the great hall as it was not expected to house so many people. It was a room of comfort and status, and usually included a fireplace and often decorative woodwork or tapestries/wall hangings.
The solar was almost ubiquitous among late castles across the British Isles, such as Broughton Castle, in Oxfordshire, and Stokesay Castle in Shropshire. In the medieval house of Great Dixter, in East Sussex, the solar is the uppermost room. It currently consists of three rooms and a late 15th century fireplace after being restored and remodelled by architect Edwin Lutyens. In Windsor Castle its walls are painted green with gold stars. the solar was sometimes a separate tower or pavilion, away from the great hall to provide more privacy to the lord and his family.
The possibly related term grianán (from Irish grian, "the sun"; often anglicised as "greenawn") was used in medieval Ireland for a sunny parlour or reception room. By extension it was used to refer to any summer palace or noble house.
Paradigm examples
In England from north to south:
- Edlingham Castle in Northumberland, castle in ruins but solar tower is mostly intact.
- Calverley Old Hall in West Yorkshire has a solar, now converted to holiday accommodation.
- Tattershall Castle, Lincolnshire, has hall and large solar block later converted into a tower.