Ynys Môn is a constituency of the House of Commons of the Parliament of the United Kingdom. It elects one Member of Parliament (MP) by the first past the post system of election. It is one of five 'protected constituencies' within the UK, with boundaries defined by the Parliamentary Constituencies Act 2020 to be fixed to those of Isle of Anglesey County Council.

Holy Island is an island on the western side of the larger Isle of Anglesey, Wales, from which it is separated by the Cymyran Strait. It is called "Holy" because of the high concentration of standing stones, burial chambers, and other religious sites on the small island. The alternative English name of the island is Holyhead Island. According to the 2011 UK Census, the population was 13,659, of whom 11,431 (84%) lived in the largest town, Holyhead.