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.
- Kaul, Chandrika. "Ritchie, Sir Richmond Thackeray Willoughby". Oxford Dictionary of National Biography (online ed.). Oxford University Press. doi:10.1093/ref:odnb/35764.(Subscription or UK public library membership required.)
- India, Select Births and Baptisms, 1786-1947
- "Ritchie, Richmond Thackeray Willoughby (RTCY874RT)". A Cambridge Alumni Database. University of Cambridge.