The islands lie some to the northeast of Orkney and southeast of the Faroe Islands and form part of the division between the Atlantic Ocean to the west and the North Sea to the east. The total area is and the population totalled 23,167 in 2011. Comprising the Shetland constituency of the Scottish Parliament, Shetland is also one of the 32 council areas of Scotland; the islands' administrative centre and only burgh is Lerwick.
The largest island, known simply as "Mainland", has an area of , making it the third-largest Scottish island and the fifth-largest of the British Isles. There are an additional 15 inhabited islands. The archipelago has an oceanic climate, a complex geology, a rugged coastline and many low, rolling hills.
Humans have lived there since the Mesolithic period, and the earliest written references to the islands date back to Roman times. The early historic period was dominated by Scandinavian influences, especially Norway, and the islands did not become part of Scotland until the 15th century. When Shetland became part of the Kingdom of Great Britain in 1707, trade with northern Europe decreased. Fishing has continued to be an important aspect of the economy up to the present day. The discovery of North Sea oil in the 1970s significantly boosted Shetland incomes, employment and public sector revenues.
The local way of life reflects the joint Norse and Scottish heritage including the Up Helly Aa fire festival, and a strong musical tradition, especially the traditional fiddle style. The islands have produced a variety of writers of prose and poetry, many of whom use the local Shetlandic dialect. There are numerous areas set aside to protect the local fauna and flora, including a number of important seabird nesting sites.
Due to the practice, dating to at least the early Neolithic, of building in stone on virtually treeless islands, Shetland is extremely rich in physical remains of the prehistoric eras and there are over 5,000 archaeological sites all told. A midden site at West Voe on the south coast of Mainland, dated to 4320–4030 BC, has provided the first evidence of Mesolithic human activity on Shetland. The same site provides dates for early Neolithic activity and finds at Scord of Brouster in Walls have been dated to 3400 BC. "Shetland knives" are stone tools that date from this period made from felsite from Northmavine.
Pottery shards found at the important site of Jarlshof also indicate that there was Neolithic activity there although the main settlement dates from the Bronze Age. This includes a smithy, a cluster of wheelhouses and a later broch. The site has provided evidence of habitation during various phases right up until Viking times. Heel-shaped cairns, are a style of chambered cairn unique to Shetland, with a particularly large example on Vementry.
Numerous brochs were erected during the Iron Age. In addition to Mousa there are significant ruins at Clickimin, Culswick, Old Scatness and West Burrafirth, although their origin and purpose is a matter of some controversy. The later Iron Age inhabitants of the Northern Isles were probably Pictish, although the historical record is sparse. Hunter (2000) states in relation to King Bridei I of the Picts in the sixth century AD: "As for Shetland, Orkney, Skye and the Western Isles, their inhabitants, most of whom appear to have been Pictish in culture and speech at this time, are likely to have regarded Bridei as a fairly distant presence.” In 2011, the collective site, "The Crucible of Iron Age Shetland" including Broch of Mousa, Old Scatness and Jarlshof joined the UKs "Tentative List" of World Heritage Sites.