Richard William Alan Onslow, 5th Earl of Onslow GBE PC DL (23 August 1876 – 9 June 1945), styled Viscount Cranley until 1911, was a British peer, diplomat, parliamentary secretary and government minister.
Onslow was the son of William Onslow, 4th Earl of Onslow and the Honourable Florence Coulston Gardner. He was educated at Eton and New College, Oxford before joining the Diplomatic Service in 1901.
He became an Attaché to Madrid a year later, Third Secretary to Tangier in 1903 and to St Petersburg in 1904 and Second Secretary to Berlin in 1907. In 1909, he became assistant private secretary to Sir Edward Grey, the Secretary of State for Foreign Affairs. He then held a number of positions in the Foreign Office as a clerk in 1910, private secretary to the Under-Secretary of State for Foreign Affairs from 1911–13 and assistant clerk from 1913-14.
Onslow joined the army on the outbreak of World War I in 1914 and was mentioned in despatches three times, received an OBE and the French Legion of Honour. In later years he was Honorary Lieutenant-Colonel of the 3rd Battalion Queen's Royal Regiment (West Surrey) and Honorary Colonel of the 30th (Surrey) Searchlight Regiment, Royal Artillery.