Cliodhna Manning is a former Irish national 400 metres champion, winning the title in 2017 with Kilkenny City Harriers.
She travelled to the Tokyo 2020 Olympic Games as a reserve for Ireland's mixed 4x400 metres relay team, named in the six-person panel for the event. The team reached the final and finished eighth.
Manning returned to the sport in 2021 after a series of injuries had kept her out of competition for several years, training on grass in Kilkenny's Castle Park during the Covid-19 pandemic while completing a master's degree at IT Carlow. She won her heat and finished second in the 400 metres at the 2021 national championships behind Phil Healy, a performance that brought her to the selection committee's attention. She went on to compete in the women's 4x400 metres relay at the 2025 European Athletics Indoor Championships in Apeldoorn. She is from Kilkenny and is a member of Kilkenny City Harriers.