Second World War: RMS Lancastria was sunk by German aircraft near Saint-Nazaire, France, causing thousands of fatalities in Britain's worst maritime disaster.

World War II or the Second World War was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated, with many nations mobilising all resources in pursuit of total war. Tanks and aircraft played major roles, enabling the strategic bombing of cities and delivery of the first and only nuclear weapons ever used in war. World War II is the deadliest conflict in history, causing the death of 70 to 85 million people, more than half of whom were civilians. Millions died in genocides, including the Holocaust, and by massacres, starvation, and disease. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were tried for war crimes.

RMS Lancastria was a British ocean liner requisitioned by the Government of the United Kingdom during the Second World War. She was sunk on 17 June 1940 during Operation Aerial. Having received an emergency order to evacuate British nationals and troops from France, the ship was loaded well in excess of its capacity of 1,300 passengers. Modern estimates suggest that between 4,000 and 7,000 people died during the sinking — the largest single-ship loss of life in British maritime history.

Saint-Nazaire is a commune in the Loire-Atlantique department in western France, in traditional Brittany.