William Nassau Molesworth
William Nassau Molesworth (1816–90) was an English clergyman and historian.
He was the eldest son of the Rev. John Edward Nassau Molesworth, vicar of Rochdale, Lancashire, by the vicar's first wife. William was born 8 November 1816, at Millbrook, near Southampton, where his father then held a curacy. He was educated at the King's School, Canterbury, and at St. John's College, Cambridge and Pembroke College, Cambridge, where as a senior optime, he graduated B.A. in 1839. In 1842, he proceeded to the degree of M.A., and in 1883 the university of Glasgow bestowed on him its LL.D. degree. 
He was ordained in 1839, and became curate to his father at Rochdale, but in 1841 the wardens and fellows of the Manchester Collegiate Church presented him to the incumbency of St. Andrew's Church, Travis Street, Ancoats, in Manchester, and in 1844 his father presented him to the church of St. Clement, Spotland, near Rochdale, which living he held till his resignation through ill-health in 1889. 
Though a poor preacher, he was a zealous and earnest parish priest ; and in 1881 his labours were rewarded by an honorary canonry in Manchester Cathedral, conferred on him by Bishop Fraser. Ecclesiastically he was a high churchman; politically a radical. He was the friend of John Bright, who publicly praised one of his histories, and of Richard Cobden, and received information from Lord Brougham for his History of the Reform Bill. He was among the first to support the co-operative movement, which he knew through the 'Rochdale Pioneers.'  He served as President of the second day of the 1870 Co-operative Congress, the second to take place.
Though described as 'angular in manner,' he appears to have been agreeable and estimable in private life. After some years of ill-health, he died at Rochdale 19 December 1890, and was buried at Spotland. 
He married, 3 September 1844, Margaret, daughter of George Murray of Ancoats Hall, Manchester, by whom he had six sons and one daughter.
Molesworth wrote a number of political and historical works, 'rather annals than history,' but copious and accurate. His principal work was History of England from 1830 [to the date of publication], 1871-3, and incorporating an earlier work on the Reform Bill ; it reached a fifth thousand in 1874, and an abridged edition was published in 1887. His other works were :
- Essay on the Religious Importance of Secular Instruction, 1857.
- Essay on the French Alliance, which in 1860 gained the Emerton prize adjudicated by Lords Brougham, Clarendon, and Shaftesbury.
- Plain Lectures on Astronomy, 1862.
- History of the Reform Bill of 1832, 1864.
- History of the Church of England from 1660, 1882. 
He also edited, with his father, Common Sense, 1842-3.
This article incorporates text from a publication now in the public domain: Hamilton, John Andrew (1894). "Molesworth, William Nassau". In Lee, Sidney. Dictionary of National Biography. 38. London: Smith, Elder & Co.