The 1886 Galway Borough by-election was a parliamentary by-election held for the United Kingdom House of Commons constituency of Galway Borough on 11 February 1886. The seat had been won by T. P. O'Connor of the Irish Parliamentary Party in the general election of 1885, but having been elected also in Liverpool Scotland, he chose to sit for the latter. The Galway seat thus became vacant, requiring a by-election.

Captain William Henry O'Shea was an Irish soldier and Member of Parliament. He is best known for being the ex-husband of Katharine O'Shea, the long-time mistress of the Irish nationalist leader Charles Stewart Parnell.