Of his appointment, Reidie said: "Sanford is a great business. Its people are highly engaged and motivated and I can't wait to join them in 2021.
"I have fresh perspectives to bring to Sanford and I am clear on my mission. I welcome the challenge of navigating the business and its people through the current volatile conditions, while working towards a long-term vision to grow sustainable shareholder returns."
An exact start date for Reidie will be announced in the New Year.
Andre Gargiulo, who has been acting chief executive since September, would continue in the role until Reidie starts.
Former chief executive Volker Kuntzsch announced he would step down from the top job in September after seven years leading the company.
Sanford's share rose 3c to $4.95 on the appointment announcement but are down 37.88 per cent over the last year.