Ewing most recently worked for Nasdaq, where she held several senior executive roles, including chief information officer.
At Nasdaq, she was responsible for the planning, delivery and operational support for all Nasdaq technology systems and infrastructure.
Ewing also serves on the boards of the New York Hall of Science and the Nasdaq Entrepreneurial Center.
Charles Gregson, chair of NEX Group, commented: "On behalf of the board I am delighted to welcome Anna Ewing to NEX. She brings significant technology and operations experience to NEX, which I am confident, will support our development and growth as a financial technology company. I look forward to working with Ewing on the board."
Ewing added: “This is an exciting time to be joining NEX. I believe that my previous experience at Nasdaq, CIBC and Merrill Lynch will be directly relevant to NEX as a financial technology company. I am looking forward to getting to work with the other board members.”