Henry John Temple, 3rd Viscount Palmerston, KG, GCB, PC (20 October 1784 – 18 October 1865), known popularly as Lord Palmerston, is a British statesman who serves twice as Prime Minister in the mid-19th century.

Popularly nicknamed "The Mongoose", he is in government office almost continuously from 1807 until his death in 1865, beginning his parliamentary career as a Tory and concluding it as a Liberal.

He is best remembered for his direction of British foreign policy through a period when Britain is at the height of its power, serving terms as both Foreign Secretary and Prime Minister.

Some of his aggressive actions, now sometimes termed liberal interventionist, are greatly controversial at the time, and remain so today.

He is the most recent British Prime Minister to die in office.