Somaliland, officially the Republic of Somaliland, is an unrecognised de facto sovereign state in the Horn of Africa, still considered internationally to be part of Somalia. Somaliland lies in the Horn of Africa, on the southern coast of the Gulf of Aden. It is bordered by Djibouti to the northwest, Ethiopia to the south and west, and Somalia to the east. Its claimed territory has an area of 176,120 square kilometres (68,000 sq mi), with approximately 5.7 million residents as of 2021. The capital and largest city is Hargeisa. The government of Somaliland regards itself as the successor state to British Somaliland, which, as the briefly independent State of Somaliland, united from 1960 to 1991 with the Trust Territory of Somaliland (the former Italian Somaliland) to form the Somali Republic.

The area of Somaliland was inhabited around 10,000 years ago during the Neolithic age. The ancient shepherds raised cows and other livestock and created vibrant rock art paintings. Throughout the Middle Ages, Arab immigrants arrived in Somaliland, including the Muslim sheikhs Ishaaq bin Ahmed, who founded the Isaaq clan, and Abdirahman bin Isma'il al-Jabarti who founded the Darod clan, who both travelled from Arabia to Somaliland and married into the local Dir clan, which have been described as legendary stories. Also during the Middle Ages, Somali empires dominated the regional trade, including the Sultanate of Ifat and the Adal Sultanate.

In the 18th century, the Isaaq Sultanate, a Somali successor state to the Adal Sultanate, was established by Sultan Guled Abdi at Toon. The sultanate spanned parts of the Horn of Africa and covered most of modern-day Somaliland. It had a robust economy and trade was significant at its main port of Berbera and the smaller port town of Bulhar, as well as eastwards at the frankincense-exporting port towns of Heis, Karin, and El-Darad.

In the late 19th century, the United Kingdom signed agreements with the Habr Awal, Garhajis, Habr Je'lo, Warsangeli, Issa and Gadabuursi clans establishing a protectorate.

The Dervishes led by Muhammad Abdullah Hassan were against the protection agreements signed with Britain with the Somali sultans. After a span of 20 years, the Dervishes were finally defeated in one of the first aerial bombardments in Africa in 1920 Somaliland Campaign. The largest of the clans, the Dhulbahante, who did not sign a treaty of protection with the British (due to the fact that the Italians considered part of the Dhulbahante as subjects of the Italian-protected Sultan of the Majeerteen clan) were the foremost proponents of the movement.

On 26 June 1960, the protectorate gained independence as the State of Somaliland, before five days later voluntarily uniting with the Trust Territory of Somaliland, following its separate independence, to form the Somali Republic. A lawful union occurred between the two territories through their elected representatives. On 27 June 1960, the Legislative Assembly of Somaliland unanimously enacted an Act of Union with Somalia which stated that the two entities would forever remain united.

In 1961, Somalia took control of state institutions, which was rejected in the former State of Somaliland and resulted in the Somaliland residents boycotting the vote on the Somali constitution. In December 1961, the revolt in the north was started by soldiers of the former State of Somaliland who took control of large cities in the north. A group of officers took control of the radio station in Hargeisa, declaring the end of the unity between Somalia and Somaliland.

In April 1981 the Somali National Movement (SNM) was founded, which led to the Somaliland War of Independence. In 1988, at the height of the war, the regime in Somalia under the dictator Siad Barre began a crackdown against the Hargeisa-based SNM and other militant groups, which were among the events that led to the Somali Civil War. The conflict left Somalia's economic and military infrastructure severely damaged. Following the collapse of Barre's regime in early 1991, local authorities, led by the SNM, unilaterally declared independence from Somalia on 18 May of the same year and reinstated the borders of the former short-lived independent State of Somaliland.

Since 1991, the territory has been governed by democratically elected governments that seek international recognition as the government of the Republic of Somaliland. The central government maintains informal ties with some foreign governments, who have sent delegations to Hargeisa. Somaliland is currently recognized by the Republic of China (Taiwan) and hosts representative offices from several other countries, most notably Ethiopia. However, Somaliland's self-proclaimed independence has not been officially recognised by any UN member state or international organisation. It is the largest unrecognized state in the world by de facto controlled land area. It is a member of the Unrepresented Nations and Peoples Organization, an advocacy group whose members consist of indigenous peoples, minorities and unrecognised or occupied territories.