John Jones (10 November 1766 – 21 May 1821), better known by his bardic name Jac Glan-y-gors, was a Welsh language satirical poet and radical pamphleteer, born in Cerrigydrudion, Denbighshire, north Wales.

His best known prose works are Seren Tan Gwmmwl and Toriad y Dydd, political tracts addressed to the Welsh people which reflect the radical ideals of Thomas Paine and the author's Welsh patriotism.

[2] His poetic output is more considerable and includes the poem entitled Cerdd Dic Siôn Dafydd[Note 1] which lampoons those of the upwardly-mobile Welsh in London who turned their backs on their country and language in order to ingratiate themselves to the English.

The eponymous 'Dic Siôn Dafydd' has entered common usage as a derogatory term for any Welsh person of a similar nature, rather like "Uncle Tom" in relation to Afro-Americans.

On 23 July 1816, he married Jane Mondel of Whitehaven in Bermondsey parish church.