# Ynys Môn (Senedd constituency)

Ynys Môn is a constituency of the Senedd. It elects one Member of the Senedd by the first past the post method of election. Ynys Môn is also one of nine constituencies in the North Wales electoral region, which elects four additional members, in addition to nine constituency members, to produce a degree of proportional representation for the region as a whole.
It was represented from 1999 by Ieuan Wyn Jones, the former leader of Plaid Cymru. Jones resigned from the Assembly on 20 June 2013, triggering a by-election, which was held on 1 August 2013. Plaid Cymru's candidate Rhun ap Iorwerth comfortably held the seat for the party with a majority of over 9000 votes.

## Boundaries

The constituency was created for the first election to the Assembly, in 1999, with the name and boundaries of the Ynys Môn Westminster constituency. It is entirely within the preserved county of Gwynedd.
As created in 1999, the North Wales region includes the constituencies of Alyn and Deeside, Caernarfon, Clwyd West, Clwyd South, Conwy, Delyn, Vale of Clwyd, Wrexham and Ynys Môn. From the 2007 Assembly election the region included Aberconwy, Alyn and Deeside, Arfon, Clwyd South, Clwyd West, Delyn, Vale of Clwyd, Wrexham and Ynys Môn.

## Voting

In elections for the Senedd, each voter has two votes. The first vote may be used to vote for a candidate to become the Assembly Member for the voter's constituency, elected by the first past the post system. The second vote may be used to vote for a regional closed party list of candidates. Additional member seats are allocated from the lists by the d'Hondt method, with constituency results being taken into account in the allocation.

## Assembly Members and Members of the Senedd

| Election | Election | Member | Party |
| | 1999 | Ieuan Wyn Jones | Plaid Cymru |
| | 2013 by-election | Rhun ap Iorwerth | Plaid Cymru |

## Elections
### Elections in the 2020s

2021 Senedd election: Ynys Môn :
| Party | Party | Candidate | Constituency | Constituency | Constituency | Regional | Regional | Regional |
| Party | Party | Candidate | Votes | % | ±% | Votes | % | ±% |
| | Plaid Cymru | Rhun ap Iorwerth | 15,506 | 55.9 | +1.1 | 11,892 | 42.7 | -1.3 |
| | Conservative | Lyn Hudson | 5,689 | 20.5 | +9.0 | 6,199 | 22.3 | +8.6 |
| | Labour | Sam Egelstaff | 5,300 | 19.1 | +2.1 | 6,546 | 23.5 | +5.1 |
| | Reform UK | Emmett Jenner | 692 | 2.5 | New | 352 | 1.26 | New |
| | Liberal Democrats | Christopher Jones | 547 | 2.0 | +0.7 | 478 | 1.7 | -0.6 |
| | Abolish | Abolish | Abolish | Abolish | Abolish | 739 | 2.7 | -1.6 |
| | Green | Green | Green | Green | Green | 734 | 2.6 | +0.3 |
| | UKIP | UKIP | UKIP | UKIP | UKIP | 371 | 1.3 | -12.4 |
| | Gwlad | Gwlad | Gwlad | Gwlad | Gwlad | 202 | 0.7 | New |
| | Freedom Alliance (UK) | Freedom Alliance (UK) | Freedom Alliance (UK) | Freedom Alliance (UK) | Freedom Alliance (UK) | 122 | 0.4 | New |
| | Communist | Communist | Communist | Communist | Communist | 77 | 0.3 | ±0.0 |
| | Propel | Propel | Propel | Propel | Propel | 50 | 0.2 | New |
| | TUSC | TUSC | TUSC | TUSC | TUSC | 14 | 0.1 | New |
| | Independent | Michelle Brown | Michelle Brown | Michelle Brown | Michelle Brown | 13 | 0.1 | New |
| Majority | Majority | Majority | 10,206 | 35.4 | −2.4 |
| Turnout | Turnout | Turnout | 27,734 | | |
| | Plaid Cymru hold | Plaid Cymru hold | Swing | | |
| Notes ↑ Incumbent member for this constituency |||||||||

### Elections in the 2010s

Welsh Assembly Election 2016: Ynys Môn :
| Party | Party | Candidate | Constituency | Constituency | Constituency | Regional | Regional | Regional |
| Party | Party | Candidate | Votes | % | ±% | Votes | % | ±% |
| | Plaid Cymru | Rhun ap Iorwerth | 13,788 | 54.8 | +13.4 | 11,015 | 44.0 | +8.2 |
| | Labour | Julia Dobson | 4,278 | 17.0 | -9.2 | 4,598 | 18.4 | -4.7 |
| | UKIP | Simon Wall | 3,212 | 12.8 | N/A | 3,417 | 13.7 | +7.8 |
| | Conservative | Clay Theakston | 2,904 | 11.5 | -17.7 | 3,430 | 13.7 | -10.7 |
| | Green | Gerry Wolff | 389 | 1.5 | New | 577 | 2.3 | +0.3 |
| | Liberal Democrats | Thomas Crofts | 334 | 1.3 | - 1.9 | 578 | 2.3 | ±0.0 |
| | Independent | Daniel ap Eifion Jones | 262 | 1.0 | New |
| | Abolish | Abolish | Abolish | Abolish | Abolish | 1,066 | 4.3 | New |
| | Monster Raving Loony | Monster Raving Loony | Monster Raving Loony | Monster Raving Loony | Monster Raving Loony | 146 | 0.6 | New |
| | Association of Welsh Independents | Association of Welsh Independents | Association of Welsh Independents | Association of Welsh Independents | Association of Welsh Independents | 94 | 0.4 | New |
| | Communist | Communist | Communist | Communist | Communist | 63 | 0.3 | +0.1 |
| | Mark Young - Independent | Mark Young - Independent | Mark Young - Independent | Mark Young - Independent | Mark Young - Independent | 48 | 0.2 | New |
| Majority | Majority | Majority | 9,510 | 37.8 | +25.6 |
| Turnout | Turnout | Turnout | 25,167 | 50.0 | +1.4 |
| | Plaid Cymru hold | Plaid Cymru hold | Swing | | |
2013 Ynys Môn by-election :
| Party | Party | Candidate | Votes | % | ±% |
| | Plaid Cymru | Rhun ap Iorwerth | 12,601 | 58.24 | +16.8 |
| | Labour | Tal Michael | 3,435 | 15.88 | −10.3 |
| | UKIP | Nathan Gill | 3,099 | 14.3 | New |
| | Conservative | Neil Fairlamb | 1,843 | 8.5 | −20.7 |
| | Socialist Labour | Kathrine Jones | 348 | 1.6 | New |
| | Liberal Democrats | Stephen Churchman | 309 | 1.4 | −1.8 |
| Majority | Majority | Majority | 9,166 | 42.3 | +30.1 |
| Turnout | Turnout | Turnout | 21,635 | 42.4 | −6.2 |
| | Plaid Cymru hold | Plaid Cymru hold | Swing | +13.58 | |
Welsh Assembly Election 2011: Ynys Môn :
| Party | Party | Candidate | Constituency | Constituency | Constituency | Regional | Regional | Regional |
| Party | Party | Candidate | Votes | % | ±% | Votes | % | ±% |
| | Plaid Cymru | Ieuan Wyn Jones | 9,969 | 41.4 | +1.7 | 8,620 | 35.8 | -6.2 |
| | Conservative | Paul Williams | 7,032 | 29.2 | +16.2 | 5,875 | 24.4 | +3.3 |
| | Labour | Joe Lock | 6,307 | 26.2 | +8.8 | 5,552 | 23.1 | +3.5 |
| | Liberal Democrats | Rhys Taylor | 759 | 3.2 | -0.2 | 554 | 2.3 | -0.4 |
| | UKIP | UKIP | UKIP | UKIP | UKIP | 1,431 | 5.9 | +1.3 |
| | Green | Green | Green | Green | Green | 481 | 2.0 | -2.6 |
| | Socialist Labour | Socialist Labour | Socialist Labour | Socialist Labour | Socialist Labour | 732 | 3.0 | +2.1 |
| | BNP | BNP | BNP | BNP | BNP | 539 | 2.2 | -1.3 |
| | Weyman - Independent | Weyman - Independent | Weyman - Independent | Weyman - Independent | Weyman - Independent | 105 | 0.4 | New |
| | Welsh Christian | Welsh Christian | Welsh Christian | Welsh Christian | Welsh Christian | 104 | 0.4 | -0.2 |
| | Communist | Communist | Communist | Communist | Communist | 59 | 0.2 | -0.1 |
| Majority | Majority | Majority | 2,937 | 12.2 | −4.2 |
| Turnout | Turnout | Turnout | 24,067 | 48.6 | −3.2 |
| | Plaid Cymru hold | Plaid Cymru hold | Swing | -7.3 | |
Regional ballots rejected at the count: 144

### Elections in the 2000s

Welsh Assembly Election 2007: Ynys Môn :
| Party | Party | Candidate | Constituency | Constituency | Constituency | Regional | Regional | Regional |
| Party | Party | Candidate | Votes | % | ±% | Votes | % | ±% |
| | Plaid Cymru | Ieuan Wyn Jones | 10,653 | 39.7 | +2.3 | 11,167 | 42.0 | +7.1 |
| | Independent | Peter Rogers | 6,261 | 23.3 | New |
| | Labour | Jonathan Austin | 4,681 | 17.4 | -6.4 | 5,212 | 19.6 | -5.6 |
| | Conservative | James Roach | 3,480 | 13.0 | -15.5 | 5,612 | 21.1 | -2.9 |
| | Liberal Democrats | Mandi Abrahams | 912 | 3.4 | -4.8 | 723 | 2.7 | -6.8 |
| | UKIP | Francis Wykes | 833 | 3.1 | +2.2 | 1,221 | 4.6 | +2.1 |
| | Green | Green | Green | Green | Green | 1,217 | 4.6 | +2.6 |
| | BNP | BNP | BNP | BNP | BNP | 934 | 3.5 | New |
| | Socialist Labour | Socialist Labour | Socialist Labour | Socialist Labour | Socialist Labour | 234 | 0.9 | New |
| | Welsh Christian | Welsh Christian | Welsh Christian | Welsh Christian | Welsh Christian | 148 | 0.6 | New |
| | Communist | Communist | Communist | Communist | Communist | 77 | 0.3 | New |
| | CPA | CPA | CPA | CPA | CPA | 50 | 0.2 | New |
| Majority | Majority | Majority | 4,392 | 16.4 | +6.5 |
| Turnout | Turnout | Turnout | 26,820 | 51.8 | +1.5 |
| | Plaid Cymru hold | Plaid Cymru hold | Swing | | |
Welsh Assembly Election 2003: Ynys Môn :
| Party | Party | Candidate | Constituency | Constituency | Constituency | Regional | Regional | Regional |
| Party | Party | Candidate | Votes | % | ±% | Votes | % | ±% |
| | Plaid Cymru | Ieuan Wyn Jones | 9,452 | 37.4 | -15.2 | 8,765 | 34.9 | -12.1 |
| | Conservative | Peter Rogers | 7,197 | 28.5 | +9.3 | 6,025 | 24.0 | +5.0 |
| | Labour | William Gerwyn Jones | 6,024 | 23.8 | +0.9 | 6,342 | 25.2 | -0.4 |
| | Liberal Democrats | Nicholas Bennett | 2,089 | 8.2 | +3.0 | 2,381 | 9.5 | +3.7 |
| | UKIP | Francis Charles Wykes | 481 | 1.9 | New | 616 | 2.5 | New |
| | Green | Green | Green | Green | Green | 509 | 2.0 | Unknown |
| | John Marek Independent Party | John Marek Independent Party | John Marek Independent Party | John Marek Independent Party | John Marek Independent Party | 219 | 0.9 | New |
| | Cymru Annibynnol | Cymru Annibynnol | Cymru Annibynnol | Cymru Annibynnol | Cymru Annibynnol | 171 | 0.7 | New |
| | Communist | Communist | Communist | Communist | Communist | 58 | 0.2 | Unknown |
| | ProLife Alliance | ProLife Alliance | ProLife Alliance | ProLife Alliance | ProLife Alliance | 33 | 0.1 | New |
| Majority | Majority | Majority | 2,255 | 8.9 | −20.8 |
| Turnout | Turnout | Turnout | 25,243 | 50.3 | −9.3 |
| | Plaid Cymru hold | Plaid Cymru hold | Swing | | |
2003 Electorate: 49,998 Regional ballots rejected: 239

### Elections in the 1990s

Welsh Assembly Election 1999: Ynys Môn :
| Party | Party | Candidate | Constituency | Constituency | Constituency | Regional | Regional | Regional |
| Party | Party | Candidate | Votes | % | ±% | Votes | % | ±% |
| | Plaid Cymru | Ieuan Wyn Jones | 16,469 | 52.6 | N/A | 14,664 | 47.0 | N/A |
| | Labour | Albert Owen | 7,181 | 22.9 | N/A | 7,982 | 25.6 | N/A |
| | Conservative | Peter Rogers | 6,031 | 19.2 | N/A | 5,930 | 19.0 | N/A |
| | Liberal Democrats | James Clarke | 1,630 | 5.2 | N/A | 1,816 | 5.8 | N/A |
| | Green | Green | Green | Green | Green | Unknown | Unknown | N/A |
| | Rhuddlan Debt Protest Campaign | Rhuddlan Debt Protest Campaign | Rhuddlan Debt Protest Campaign | Rhuddlan Debt Protest Campaign | Rhuddlan Debt Protest Campaign | Unknown | Unknown | N/A |
| | United Socialist | United Socialist | United Socialist | United Socialist | United Socialist | Unknown | Unknown | N/A |
| | Communist | Communist | Communist | Communist | Communist | Unknown | Unknown | N/A |
| | Natural Law | Natural Law | Natural Law | Natural Law | Natural Law | Unknown | Unknown | N/A |
| | Above list parties | Above list parties | Above list parties | Above list parties | Above list parties | 784 | 2.5 | N/A |
| Majority | Majority | Majority | 9,288 | 29.7 |
| Turnout | Turnout | Turnout | 31,311 | 59.6 |
| | Plaid Cymru win (new seat) | Plaid Cymru win (new seat) | Plaid Cymru win (new seat) | Plaid Cymru win (new seat) | Plaid Cymru win (new seat) |