William Grenville, 1st Baron Grenville, English academic and politician, Prime Minister of the United Kingdom (born 1759)

William Wyndham Grenville, 1st Baron Grenville was a British Pittite Tory politician who was Prime Minister of the United Kingdom from 1806 to 1807, but was a supporter of the Whigs for the duration of the Napoleonic Wars. As prime minister, his most significant achievement was the abolition of the slave trade in 1807. However, his government failed to either make peace with France or to accomplish Catholic emancipation and it was dismissed in the same year.

The prime minister of the United Kingdom is the head of government of the United Kingdom. The prime minister advises the sovereign on the exercise of much of the royal prerogative, chairs the Cabinet, and selects its ministers. Modern prime ministers hold office by virtue of their ability to command the confidence of the House of Commons, so they are invariably members of Parliament.