Sir Charles Kingsley Webster KCMG FBA (25 July 1886 – August 1961) was a British diplomat and historian.

After leaving Cambridge University, he went on to become a professor at Harvard, Oxford, and the London School of Economics (LSE).

After studying at Cambridge, Webster became professor of international relations at the University of Wales, Aberystwyth where he wrote his two major books on the foreign policy of Lord Castlereagh, the first (published in 1925) covering the period 1815–1822, the second (published in 1931) that from 1812 to 1815.

In 1932 Webster moved to the newly established Stevenson chair of international relations at the LSE.

In 1951, his biography of Henry John Temple, 3rd Viscount Palmerston was finally published.