Henry Landau OBE (7 March 1892 – 20 May 1968) was a South African World War I volunteer who served with the British Army's Royal Field Artillery when he was recruited into what is now known as the SIS (MI6).

After sick leave in London and a dinner date with one of the secretaries of the head of MI6, Royal Navy Captain Mansfield Smith-Cumming (the original "C"), Landau was recruited and sent to the MI6 station in Rotterdam.

His biggest success would be the handling of La Dame Blanche, a group of more than a thousand Belgian and French agents who monitored the movement of German troop trains to and from the Western Front.

Not able to deal with bureaucracy and boredom, he resigned the military in 1920 and took employment procuring patents and inventions for a British shipbuilding company.

In the book, All's Fair, he revealed the existence of Karl Krüger, a former officer in the German Imperial Navy, who was one of MI6's most important World War I spies.