Brigadier James Roderick Sinclair, 19th Earl of Caithness, CVO, CBE, DSO (29 September 1906 – 8 May 1965) was a British Army officer during World War II, hereditary peer and chief of Clan Sinclair.

Sinclair joined the Gordon Highlanders and rose to the rank of Brigadier and as such led his regiment (part of the 51st (Highland) Division) through France, Belgium, the Netherlands into Germany during World War II and was decorated with the Distinguished Service Order (DSO) and made Commander of the Order of the British Empire (CBE).

On returning to the UK he was given various postings in England and Scotland before in 1955 being appointed land agent and manager of Her Majesty The Queen's private Estate at Balmoral Castle, Aberdeenshire where he lived until his death.

In 1946, he married secondly a widow Madeline Gabrielle Ormerod (nee de Pury) (1912–1990), whose husband had been killed on active service in Africa leaving her with a daughter (Susie).

He was succeeded in the earldom and its subsidiary titles and as chief of Clan Sinclair by his only son, Malcolm.