The Bassetlaw by-election, 1890 was a parliamentary by-election held for the British House of Commons constituency of Bassetlaw in Nottinghamshire on 15 December 1890.
The by-election was caused by the death of the sitting Conservative MP, William Beckett-Denison on 23 November 1890. Beckett-Denison had won the newly created seat at the 1885 general election.
The Conservative party selected Sir Frederick Milner, son-in-law of the deceased MP and former member for York, as their candidate. Milner's candidature was supported by Francis Foljambe, a Liberal Unionist and former MP for the area, who had been defeated by Beckett-Denison in the 1885 election. The Liberal candidate was John William Mellor, former MP for Grantham.
Campaigning was lively. "The constituency is being flooded with literature of every description", reported the Times. Women campaigners were active, from the Conservative Primrose League and the Women's Liberal association who were reported to be 'taking a Home Rule van through the district'.
The Home Rule issue was a difficult one for the Liberals at this precise moment, with a split in the Irish Parliamentary Party taking place over the continued leadership of Charles Stewart Parnell, following a crisis over the divorce of his partner Katharine O'Shea; Liberal leader William Gladstone had warned the party that Parnell's continued leadership would mean the end of prospects of Home Rule. At a public meeting in the Constituency, the Conservative MP for North Armagh, Edward James Saunderson, made fun of Gladstone's difficulties: "in 1886, a marriage was consummated between Mr Gladstone and his followers and Mr Parnell and his friends. Since then, however, there had been a divorce (cheers and laughter), and ... they had discovered that all the love was on one side". The issue was picked up in a later speech by the Liberal Unionist MP for Tyrone South Thomas Russell: "he would ask his fellow Nonconformists not to submit the Presbyterians, Methodists and Independents of Ireland to the shame and humiliation of being governed by a man who was a convicted adulterer and liar, and whose conduct, he regretted to say, was practically condoned by the Liberal party".