Most recently she was made the director of womenswear, lingerie, footwear and accessories at Target Australia in 2014, where she spent a year at the business.
Whittle, joins the womenswear brand at the time which sees the business struggling as Topshop and Topman have both reported pre-tax losses of over £505m for the year to September 2018.
This followed a loss of nearly £4m for the previous year.
Paul Price, CEO of Topshop and Topman said: “We are delighted to welcome Gillian Ridley Whittle to the Topshop Topman leadership team as Topshop’s fashion director.
“Over the past 20 years, Gillian has established herself as a leader in the international womenswear industry, most recently as group general manager at two of Australia’s largest department stores, having started her career at Debenhams, followed by a decade in womenswear at Marks and Spencer in the UK.”
He added: “Gillian’s appointment is an exciting milestone for the brand. The teams look forward to working with and supporting her in further elevating and strengthening Topshop’s product proposition.”