Sir William Molesworth, 8th Baronet, PC (23 May 1810 – 22 October 1855) was a Radical British politician, who served in the coalition cabinet of The Earl of Aberdeen from 1853 until his death in 1855 as First Commissioner of Works and then Secretary of State for the Colonies.

Much later, when justifying to the Queen his own new appointments, Gladstone told her: "For instance, even in Ld Aberdeen's Govt, in 52, Sir William Molesworth had been selected, at that time, a very advanced Radical, but who was perfectly harmless, & took little, or no part...

Through Charles Buller he made the acquaintance of George Grote and James Mill, and in April 1835 he founded, in conjunction with Roebuck, the London Review, as an organ of the Philosophic Radicals.

From 1837 to 1841 Molesworth sat for Leeds, and acquired considerable influence in the House of Commons by his speeches and by his tact in presiding over the select committee on penal transportation.

[4] In 1839 he commenced and carried to completion, at a cost of £6,000, a reprint of the entire miscellaneous and voluminous writings of Thomas Hobbes, which were placed in most of the English university and provincial libraries.

The philanthropist John Passmore Edwards installed a likeness of Sir William Molesworth as a memorial medallion in the Borough Road public library in Southwark as a mark of appreciation such that, "In so doing, we gratefully remember illustrious and useful lives into whose labours we have entered, and keep before us examples worthy of admiration.