Diana Armstrong (born February 1961) is a Northern Irish Ulster Unionist Party (UUP) politician who has been a Member of the Legislative Assembly (MLA) for Fermanagh and South Tyrone since September 2024.

[2] She was co-opted onto Fermanagh and Omagh District Council in June 2016, following Rosemary Barton's election to the Northern Ireland Assembly, where she represented the Erne North District.

[4] Armstrong was the UUP candidate for Fermanagh and South Tyrone in the 2024 general election, the most marginal seat in the United Kingdom with a Sinn Féin majority of just 56 votes over the UUP.

[6] On 27 September 2024, Armstrong was co-opted to replace Tom Elliott as Member of the Legislative Assembly (MLA) for Fermanagh and South Tyrone, after he was given a peerage in July as part of the dissolution honours list.

[7] Armstrong spoke of the importance of farming at the UUP's 2024 party conference, stating that "We recognise that farming is the backbone of our economy and will always work for farm families and rural dwellers to strive for better opportunities, accessibility and support..."[8] She was announced by UUP leader Mike Nesbitt as the party's new Economy spokesperson.