James Horner Haslett (January 1832 - 18 August 1905) was an Irish Conservative Party politician who sat in the House of Commons of the United Kingdom from 1885 to 1886 and 1896 to 1905.
Haslett was the son of the Rev. Henry Haslett of Castlereagh, co. Down and his wife Mary Wilson daughter of John Wilson, linen merchant of Drumcroon, Coleraine. He was educated at Academical Institute Belfast and became a chemist and druggist. He was an alderman, and a Justice of the Peace (J.P.) of Belfast.
At the 1885 general election Haslett was elected Member of Parliament for Belfast West. He held the seat until 1886. He was mayor of Belfast in 1887 and knighted in the same year. He was mayor again in 1888.
He returned to the House of Commons at a by-election in January 1896 as MP for Belfast North. He was re-elected in 1900, and held the seat until his death in 1905, aged 73.
Haslett married Annie Rea of London in 1877.