The Balfour Declaration (dated 2 November 1917) was a letter from the United Kingdom's Foreign Secretary Arthur James Balfour to Walter Rothschild, 2nd Baron Rothschild, a leader of the British Jewish community, for transmission to the Zionist Federation of Great Britain and Ireland. It read:

The text of the letter was published in the press one week later, on 9 November 1917. The "Balfour Declaration" was later incorporated into both the Sèvres peace treaty with the Ottoman Empire, and the Mandate for Palestine. The original document is kept at the British Library.

The declaration was in contrast to the McMahon-Hussein correspondence, which promised the Arab independence movement control of the Middle East territories "in the limits and boundaries proposed by the Sherif of Mecca" in exchange for revolting against the Ottoman Empire.

The issuance of the Declaration had many long lasting consequences, and was a key moment in the lead-up to the Israeli–Palestinian conflict, often referred to as the world's "most intractable conflict".

The Balfour Declaration of 1926, issued by the 1926 Imperial Conference of British Empire leaders in London, was named for Lord President of the Council (and former Prime Minister of the United Kingdom) Arthur Balfour. It declared the United Kingdom and the Dominions to be

The Inter-Imperial Relations Committee, chaired by Balfour, drew up the document preparatory to its unanimous approval by the imperial premiers on 15 November 1926. It was first proposed by South African Prime Minister J. B. M. Hertzog and Canada's Prime Minister at that time, William Lyon Mackenzie King.

The Declaration accepted the growing political and diplomatic independence of the Dominions, in the years after World War I. It also recommended that the governors-general, the representatives of the King who acted for the Crown as de facto head of state in each dominion, should no longer also serve automatically as the representative of the British government in diplomatic relations between the countries. In following years, High Commissioners were gradually appointed, whose duties were soon recognised to be virtually identical to those of an ambassador. The first such British High Commissioner was appointed to Ottawa in 1928.