Sir Henry Haydn Jones (27 December 1863 – 2 July 1950) was a Welsh Liberal Party politician.
Henry (sometimes known as "Harry") Haydn Jones was born in Ruthin, Wales. He was the son of Joseph David Jones (1827–70), a schoolmaster in the town and a respected Welsh musician and composer. After the early death of his father, Haydn Jones was brought up by uncles at Towyn (now called Tywyn) where he was educated at the Board School & Academy. In 1903 he married Barbara Annie Gwendolen Davies Jones, daughter of Lewis D. Jones, a Welsh-born Chicago ironmonger and quarry owner.
In 1889 Haydn Jones was elected as one of the first members of Merionethshire County Council, representing the Towyn Urban District. A year later he was the chair of the council. He was eventually elected an Alderman. Jones continued to rise in the political world being elected as the MP for Merioneth at the January 1910 general election. He continued to serve in this role until 1945 general election, and received a knighthood in 1937.
In 1909 the Bryn Eglwys slate quarry, the Abergynolwyn estate and village and Talyllyn Railway came up for sale. Aware of the distress which would be caused by permanent closure of the quarry Sir Haydn bought the lot himself in 1911 for £5250, and became the sole owner of what became the Abergynolwyn Slate and Slab Company. In 1935 he extended his quarry ownership, leasing the Aberllefenni Slate Quarry in the neighbouring Corris district.