Ashton, who is currently chief executive of debt management business Capquest, will join in September. She will join the board at the same time. Beighton has already moved into his new position as chief operating officer.
Ashton has been at Capquest since May 2012. Prior to that she was finance director at Lloyds Banking Group and has also worked as managing director of Barclaycard International and head of retail finance at Asda.
Asos chief executive Nick Robertson said: “Helen brings an unusual combination of deep financial experience, combined with her track record in consumer facing and retail businesses.
“Helen has also been involved in significant change management situations and has demonstrated great leadership capability. We are delighted that Helen is joining us. This appointment also frees up Nick Beighton to focus completely on his operational responsibilities.”
Ashton added: “My time in financial services has been a great experience, but the role at Asos fits perfectly with what I want to do now, enabling me to build on my passion for consumer facing businesses and retail specifically".