Sir Basil Home Thomson, KCB (21 April 1861 – 26 March 1939) was a British colonial administrator and prison governor, who was head of Metropolitan Police CID during World War I. This gave him a key role in arresting wartime spies, and he was closely involved in the prosecution of Mata Hari, Sir Roger Casement and many Irish and Indian nationalists. His equating of Jews with Bolshevism led to accusations of anti-semitism. Thomson was also a successful novelist.