 Ní Shúilleabháin is a native of Carnacon near Ballyglass, County Mayo.She graduated with a first-class honours degree in Theoretical Physics from University College Dublin in 2005 and her PhD, completed with the School of Education of Trinity College Dublin in 2014, was funded by an Ussher Fellowship.She later worked as a post-primary school teacher of mathematics, physics, applied mathematics and science, and then became a member of the School of Mathematics & Statistics at University College Dublin, researching and lecturing in mathematics and maths education.