Windsoris a town andunparished areain theRoyal Borough of Windsor and MaidenheadinBerkshire,England. It is widely known as the site ofWindsor Castle, one of the official residences of theBritish Royal Family. It is immediately south of theRiver Thames, which forms its boundary withEton. The village ofOld Windsor, just over 2 miles (3km) to the south, predates what is now called Windsor by around 300 years; in the past Windsor was formally referred to asNew Windsorto distinguish the two.