Sir Richmond Thackeray Willoughby Ritchie (6 August 1854 - 12 October 1912) was a British civil servant. He spent most of his working life at the India Office, reaching the post of Permanent Under-Secretary of State for India.
He was born in Calcutta, British India, the third son of the jurist William Ritchie (1817-1862) and his wife, Augusta Charlotte Trimmer. He was educated at Eton College and Trinity College, Cambridge.
In 1877 Ritchie entered the India Office through open competition, as a junior clerk. He acted as Private Secretary to a number Under-Secretaries of State, both Parliamentary and Permanent: from 1895 to 1902 he worked for Lord George Hamilton. He then was transferred to the post of Secretary in the Political and Secret Department.