The Channel Islands are an archipelago lying between England and France, off the coast of Normandy. They are divided into two bailiwicks, Jersey and Guernsey, which contains Guernsey and also all other islands such as Sark, Aldeney and Herm. Neither is a part of the United Kingdom, but they are crown dependencies; this means the right to pass legislation belongs to its own legislative assemblies, with the assent of the crown. They are treated as a part of the United Kingdom for citizenship purposes.

Jersey has been an island for approximately 8,000 years and Guernsey for approximately 6,000. The earliest evidence of human activity dates to around 250,000 years ago, where it appears that hunters used the caves at La Cotte de St Brelade on Jersey as a base for hunting mammoth (at this time, before rising sea levels cut it off from the mainland, Jersey was a peninsula, attached to Normandy).

In the Neolithic period (starting around 4000BC) the nomadic bands of hunters who previously inhabited the island were supplanted by settled farming communities, who built large burial monuments known as dolmens. These usually consisted of three or more upright stones supporting a large flat horizontal capstone (table) and were usually covered with earth or smaller stones to form a barrow. In many cases, though, that covering has weathered away, leaving only the stone "skeleton" of the burial mound intact. The sheer number and size of these monuments suggests a significant social organisation on the island and connections with the surrounding coasts. Indeed, archeological evidence shows the island had trading links with both Brittany and England at this time.

Little is known about the islands up until the 11th century. Roman traders and officials did visit them, but it seems that settlement was sparse. The Britons (indigenous Celtic inhabitants of Britain) occupied them around the 6th century, during their migration to Brittany. It is held that Saint Helier from Tongeren in modern-day Belgium first brought Christianity to the archipelago, in the 6th century.

The Channel Islands took their individual names, which are of Norse origin, as a result of Viking activity in the area between the 9th and 10th centuries. In 933 William Longsword, Duke of Normandy seized the Cotentin; although the Normans gained control of England in 1066, they continued to rule their French possessions as a separate entity. The islands remained part of the Duchy of Normandy until 1204 when King Philip II Augustus of France conquered the rest of the duchy from King John of England; the islands, however, remained with King John and were described as being a Peculiar of the Crown. The islands are still officially considered a part of the Duchy of Normandy today, even though it no longer exists.

There were more invasions in the 14th century. In 1338 the French attacked and held some territory until 1345; Owen of Wales attacked Jersey and Guernsey in 1372 and Bertrand du Guesclin besieged Mont Orgueil in 1373. During the Wars of the Roses the French occupied Jersey, from 1461 to 1468. In 1483, however, a Papal Bull decreed that the islands would be neutral during time of war. This privilege enabled islanders to avoid being caught up in wars between France and England and reap the benefits of trade with both of them; it was respected until 1689 when it was abolished by Order in Council following the Glorious Revolution in Great Britain.

During the Wars of the Three Kingdoms, Jersey was strongly Royalist, providing refuge for Charles, Prince of Wales in 1646 and 1649 to 1650, while Presbyterian Guernsey generally favoured the parliamentary cause (although it is worth noting that Castle Cornet, on Guernsey, was the last /Royalist stronghold to fall, on 15 December 1651).

The islands acquired commercial and political interests in the North American colonies. Islanders became involved with the Newfoundland fisheries in the 17th century. Grateful for the help given to him by Jersey during his exile, Charles II gave George Carteret, Bailiff and governor of Jersey, a large grant of land in the American colonies, which he named New Jersey, now part of the United States of America. Edmund Andros of Guernsey was an early colonial governor in North America and head of the short-lived Dominion of New England.

During the Second World War, the islands were occupied by Germany and were in fact the only part of the British Commonwealth who suffered this fate. Some islanders evacuated when the British military withdrew, but the majority remained. The occupation, during 1940 to 1945, was harsh. Over 2,000 islanders were deported; Jews were sent to concentration camps. Slave labour was brought in from Russia in order to support the soldiers in building fortifications, many of which still remain. Four concentration camps were built on Alderney, where all but six of the entire population had evacuated before the Germans arrived. Of the total inmate population of these camps (roughly 6,000), over 700 died. It is impossible to say how many forced workers died on the other islands.

The Royal Navy blockaded the islands on several occasions, particularly following the allied victory in Normandy. There was considerable hunger during the occupation, especially during the last year; frantic negotiations resulted in the arrival of the Red Cross supply ship Vega in December 1944, which saved the islanders from starvation. Jersey and Guernsey were liberated on 9 May 1945; the German garrison in Alderney did not surrender until 16 May 1945 and was one of the last of the Nazi German remnants to surrender.

Following the Liberation of 1945, reconstruction led to a transformation of the economies of the islands, attracting immigration and developing tourism. The legislatures were reformed and non-party governments embarked on social programmes, aided by the incomes from offshore finance which grew rapidly from the 1960s. The islands decided not to join the European Economic Community when the UK joined and remain outside. Since the 1990s, however, declining profitability of agriculture and tourism have challenged the governments of the islands.