Ynys Môn (Welsh pronunciation: [ˌənɨs ˈmoːn]; officially called Anglesey until 1983) is a constituency of the House of Commons of the Parliament of the United Kingdom.

It is one of five 'protected constituencies' within the UK, with boundaries defined by the Parliamentary Constituencies Act 2020 to be to those of Isle of Anglesey County Council where there must be a whole number of MPs rounded up to the nearest whole number with these boundaries.

Electoral Calculus describes the seat as "Traditionalist", characterised by socially conservative Labour-inclined voters with lower levels of income and formal education.

The Act contains the following provision, which had the effect of enfranchising the shire of Anglesey: And that for this present Parliament, and all other Parliaments to be holden and kept for this Realm, one Knight shall be chosen and elected to the same Parliaments for every of the Shires of Brecknock, Radnor, Mountgomery and Denbigh, and for every other Shire within the said Country of Dominion of Wales; The earliest known results are a fragment of the 1541 returns, in which the name of the Knight of the Shire for Anglesey (as Members of Parliament from county constituencies were known before the 19th century) has been lost.

The official name of the constituency in English was Anglesey, until it was replaced by the Welsh name Ynys Môn.