William Pitt, known as William Pitt the Younger, was born in 1759, the second son of the Earl of Chatham and Hester Grenville. Educated at home due to poor health, he was admitted to Pembroke College in 1773. At Pembroke he was tutored by George Pretyman Tomline who would go on to be Pitt's Private Secretary after the 1784 General Election. Pitt graduated in 1776 and moved to Lincoln's Inn to carry on his legal education; he was called to the bar in the summer of 1780.

In the parliamentary elections of September 1780 Pitt stood as a candidate for one of the 2 University of Cambridge seats but lost. However, he entered Parliament in January 1781 as the result of winning a by-election in the pocket borough of Appleby. He was appointed Chancellor of the Exchequer in 1782, serving under Prime Minister William Petty, 2nd Earl of Shelburne. In 1783 Pitt became Prime Minister after the fall of the Fox-North Coalition. Pitt, at the age of 24, became Great Britain's youngest Prime Minister.

Pitt held the position of Prime Minister for 17 years, before being replaced by Henry Addington. During his time in office Pitt oversaw parliamentary reform, colonial reform, overhauled the country's finances and formed the Triple Alliance with Prussia and Holland in 1788. He also contended with the King's illness in 1788, whereby the King was incapacitated. In foreign affairs he endeavoured to seize St. Domingue from the French during the Haitian Revolution but was ultimately unsuccessful at the cost of many lives. In Ireland Pitt sought Acts of Union to make Ireland part of the United Kingdom but it was not until 1800 that the Acts were passed.

Pitt resigned on 16 February 1801 following the Acts of Union and although he supported the new administration he was often away from Parliament. Just 3 years later he returned as Prime Minister, taking office again on 10 May 1804. His second administration was weaker, and much shorter, as ill health took its toll. He died on 23 January 1806 and was buried in Westminster Abbey on the 22 February.

A note on Pitt's residence whilst at Pembroke: From at least June 1774-December 1776, Pitt lived in what is now known as the Thomas Gray Room, then known as Number 40 (the staircases were not alphabetised). The set comprised a keeping room with bedchamber and study. He also took rooms above, Number 39, perhaps for a servant or, according to legend, for his nurse. From December 1776-May 1777 (approximately), he kept Number 39, but instead lived in Number 12 in Old Court, on the North side (now demolished), the East staircase, the first floor chamber on the left hand, with it bedchamber over the first floor and chamber over the stiudy. After that, from June 1777, he seems to have retained a set on what is now L Staircase, on the right hand side, the first floor with its bedchamber on the same floor and 2 garrets. He used to return to Pembroke from time to time to do some reading, at least until 1780.

For a detailed account of Pitt's time at Pembroke see Pembroke College Cambridge Society Annual Gazette Number 8, 1934, pages 11-15.