William Lamb, 2nd Viscount Melbourne, PC, FRS (15 March 1779 – 24 November 1848) is a British Whig statesman who serves as Home Secretary (1830–1834) and Prime Minister (1834 and 1835–1841).

He is best known for his intense and successful mentoring of Queen Victoria, at ages 18–21, in the ways of politics.

Historians conclude that Melbourne does not rank high as a prime minister, for there were no great foreign wars or domestic issues to handle, he lacked major achievements and enunciated no grand principles.