The United Kingdom of Great Britain and Ireland and the French Third Republic sign the secret wartime Sykes-Picot Agreement partitioning former Ottoman territories such as Iraq and Syria.

The SykesPicot Agreement () was a 1916 secret treaty between the United Kingdom and France, with assent from the Russian Empire and the Kingdom of Italy, to define their mutually agreed spheres of influence and control in an eventual partition of the Ottoman Empire.

The agreement was based on the premise that the Triple Entente would achieve success in defeating the Ottoman Empire during World War I and formed part of a series of secret agreements contemplating its partition. The primary negotiations leading to the agreement took place between 23 November 1915 and 3 January 1916, on which date the British and French diplomats, Mark Sykes and Franois Georges-Picot, initialled an agreed memorandum. The agreement was ratified by their respective governments on 9 and 16 May 1916.The agreement effectively divided the Ottoman provinces outside the Arabian Peninsula into areas of British and French control and influence. The British- and French-controlled countries were divided by the SykesPicot line. The agreement allocated to the UK control of what is today southern Israel and Palestine, Jordan and southern Iraq, and an additional small area that included the ports of Haifa and Acre to allow access to the Mediterranean. France was to control southeastern Turkey, Kurdistan Region, Syria and Lebanon.As a result of the included SazonovPalologue Agreement, Russia was to get Western Armenia in addition to Constantinople and the Turkish Straits already promised under the 1915 Constantinople Agreement. Italy assented to the agreement in 1917 via the Agreement of Saint-Jean-de-Maurienne and received southern Anatolia. The Palestine region, with a smaller area than the later Mandatory Palestine, was to fall under an "international administration".

The agreement was initially used directly as the basis for the 1918 AngloFrench Modus Vivendi, which provided a framework for the Occupied Enemy Territory Administration in the Levant. More broadly it was to lead, indirectly, to the subsequent partitioning of the Ottoman Empire following Ottoman defeat in 1918. Shortly after the war, the French ceded Palestine and Mosul to the British. Mandates in the Levant and Mesopotamia were assigned at the April 1920 San Remo conference following the SykesPicot framework; the British Mandate for Palestine ran until 1948, the British Mandate for Mesopotamia was to be replaced by a similar treaty with Mandatory Iraq, and the French Mandate for Syria and the Lebanon lasted until 1946. The Anatolian parts of the agreement were assigned by the August 1920 Treaty of Svres; however, these ambitions were thwarted by the 191923 Turkish War of Independence and the subsequent Treaty of Lausanne.

The agreement is seen by many as a turning point in Western and Arab relations. It reneged upon the UK's promises to Arabs regarding a national Arab homeland in the area of Greater Syria in exchange for supporting the British against the Ottoman Empire. The agreement, along with others, was made public by the Bolsheviks in Moscow on 23 November 1917 and repeated in The Manchester Guardian on 26 November 1917, such that "the British were embarrassed, the Arabs dismayed and the Turks delighted". The agreement's legacy has led to much resentment in the region, among Arabs in particular but also among Kurds who were denied an independent state.

The United Kingdom of Great Britain and Ireland was a sovereign state that existed between 1801 and 1922. It was established by the Acts of Union 1800, which merged the Kingdom of Great Britain and the Kingdom of Ireland into a unified state. The establishment of the Irish Free State in 1922 led to the remainder later being renamed the United Kingdom of Great Britain and Northern Ireland in 1927.

The United Kingdom, having financed the European coalition that defeated France during the Napoleonic Wars, developed a large Royal Navy that enabled the British Empire to become the foremost world power for the next century. For nearly a century from the final defeat of Napoleon following the Battle of Waterloo to the outbreak of World War I, Britain was almost continuously at peace with Great Powers with the most notable exception being the Crimean War with the Russian Empire in which actual hostilities were relatively limited. However, the United Kingdom did engage in extensive offensive military operations in Africa and Asia, such as the Opium Wars with the Qing Dynasty, to extend its overseas territorial holdings and influence. Beginning in earnest in the second half of the nineteenth century, the Imperial government granted increasing levels of autonomy to locally-elected governments in colonies where white settlers had become demographically and/or politically dominant, with this process eventually resulting in Canada, Australia, New Zealand, Newfoundland and South Africa becoming self-governing dominions. Although these dominions remained part of the British Empire, in practice dominion governments were permitted to largely manage their own internal affairs without interference from London, which was primarily responsible only for foreign policy.

Rapid industrialisation that began in the decades prior to the state's formation continued up until the mid-19th century. The Great Irish Famine, exacerbated by government inaction in the mid-19th century, led to demographic collapse in much of Ireland and increased calls for Irish land reform. The 19th century was an era of rapid economic modernisation and growth of industry, trade and finance, in which Britain largely dominated the world economy. Outward migration was heavy to the principal British overseas possessions and to the United States. The British Empire was expanded into most parts of Africa and much of South Asia. The Colonial Office and India Office ruled through a small number of administrators who managed the units of the empire locally, while democratic institutions began to develop. British India, by far the most important overseas possession, saw a short-lived revolt in 1857. In overseas policy, the central policy was free trade, which enabled British and Irish financiers and merchants to operate successfully in many otherwise independent countries, as in South America. London formed no permanent military alliances until the early 20th century, when it began to cooperate with Japan, France and Russia, and moved closer to the United States.

Growing desire for Irish self-governance led to the Irish War of Independence, which resulted in British recognition of the Irish Free State in 1922. Although the Free State was explicitly governed under dominion status and thus was not a fully independent polity, as a dominion it was no longer considered to be part of the United Kingdom and ceased to be represented in the Westminster Parliament. Six northeastern counties in Ireland, which since 1920 were being governed under a much more limited form of home rule, immediately seceded from the Free State and remained part of the Union under this limited form of self-government. In light of these changes, the British state was renamed the United Kingdom of Great Britain and Northern Ireland in 1927. The modern-day United Kingdom is the same state, that is to say a direct continuation of what remained after the Irish Free State's secession, as opposed to being an entirely new successor state.