His dish of Celeriac baked in Barley and Fermented Hay with Cured and Smoked Celeriac beat ten other chefs at a cook-off at Harrods of London on 24 February.
Moriarty will go on to represent the UK and Ireland in a showdown between 20 global finalists at Expo Milan in June.
He said: “I’m absolutely thrilled to win the S.Pellegrino UK & Ireland Young Chef title and am very excited to represent the UK and Ireland in Milan. The final be a great opportunity to meet other young chefs from across the globe and I will do my best to impress - I will do the UK & Ireland proud.”
The judges, Clare Smyth MBE, Chef Patron at Restaurant Gordon Ramsay, Atul Kochhar, Chef Patron at Benares, Dan Doherty, Executive Chef at Duck & Waffle and Oliver Dunne, owner of Bon Appétit, deliberated over the finalists' dishes for four hours.
Smyth will go on to mentor Moriarty and help hone his signature dish before the final in Milan.
She said: “I’m honoured to be part of S.Pellegrino’s global search to find the best young chef talent in the world of fine dining and am looking forward to helping Mark perfect his dish before the final in Milan – I think the UK & Ireland can win this!”
The final will take place on 27 June at Expo Milan 2015. The global fair is expected to attract 20 million visitors with its theme of ‘Feeding the Planet, Energy for Life’.