Kelly has worked for the PLC for just over five years. He was a main board director at Service Graphics and part of the team that negotiated its sale to St Ives in 2006.
His industry career spans 30 years and includes senior marketing and business development roles at Colour Processing Laboratories (CPL) and Photobition. Most recently at St Ives he has worked on a corporate brand refresh and the interior design of the group's new headquarters in London.
Kelly's new business, K16, will provide business, marketing and creative consultancy.
He said he was "excited" about the potential opportunity: "I've worked across various sectors, at St Ives and in my career prior to that, and I understand what businesses can do and how they can market themselves better."
St Ives chief executives Patrick Martell said: "I thank Rob for all of his hard work during a time of huge change for the group and wish him all the very best for the future in his new venture."
Kelly will leave at the end of the month. It’s understood St Ives is considering various options regarding a replacement.