The Niedermayer–Hentig Expedition was a diplomatic mission to Afghanistan sent by the Central Powers in 1915–1916. The purpose was to encourage Afghanistan to declare full independence from the British Empire, enter World War I on the side of the Central Powers, and attack British India. The expedition was part of the Hindu–German Conspiracy, a series of Indo-German efforts to provoke a nationalist revolution in India. Nominally headed by the exiled Indian prince Raja Mahendra Pratap, the expedition was a joint operation of Germany and Turkey and was led by the German Army officers Oskar Niedermayer and Werner Otto von Hentig. Other participants included members of an Indian nationalist organisation called the Berlin Committee, including Maulavi Barkatullah and Chempakaraman Pillai, while the Turks were represented by Kazim Bey, a close confidante of Enver Pasha.
Britain saw the expedition as a serious threat. Britain and its ally, the Russian Empire, unsuccessfully attempted to intercept it in Persia during the summer of 1915. Britain waged a covert intelligence and diplomatic offensive, including personal interventions by the Viceroy Lord Hardinge and King George V, to maintain Afghan neutrality.