Wiltshire (; abbreviated Wilts) is a historic and ceremonial county in South West England with an area of 3,485 km² (1,346 square miles). It is landlocked and borders the counties of Dorset to the southwest, Somerset to the west, Hampshire to the southeast, Gloucestershire to the north, Oxfordshire to the northeast and Berkshire to the east. The county town was originally Wilton, after which the county is named, but Wiltshire Council is now based in the county town of Trowbridge. Within the county's boundary are two unitary authority areas, Wiltshire and Swindon, governed respectively by Wiltshire Council and Swindon Borough Council.

Wiltshire is characterised by its high downland and wide valleys. Salisbury Plain is noted for being the location of the Stonehenge and Avebury stone circles (which together are a UNESCO Cultural and World Heritage site) and other ancient landmarks, and as a training area for the British Army. The city of Salisbury is notable for its medieval cathedral. Swindon is the county’s largest town and commercial centre, with a population of 230,000. Large country houses open to the public include Longleat (where there is also a safari park) and the National Trust's Stourhead.