The collections will reflect Gok's philosophy of making women feel confident, stylish and positive about their bodies, whatever their size or shape.
Gok Wan said: "I can't wait to get started; this is a first for me. While I've styled thousands of women over the years, soon millions of women are going to be able to wear something I've created."
Luke Jensen, Sainsbury's non-food managing director, said: "TU clothing has become a major growth area for Sainsbury's, based on the concept of delivering style and quality, at affordable prices.
"Over the next few years we will continue to dedicate more space to clothing, with new store openings and the development of existing sites. As we continue to grow and expand our ranges, we're delighted to bring Gok's unique talent, as a democratiser of style and fashion, to our millions of customers. We're looking forward to working with Gok and to learning new ways to make our shoppers look and feel fantastic."
Sainsbury's launched its Tu clothing range in September 2004. The brand now accounts for 3% of all clothing, footwear and accessory sales in the UK, spanning womenswear, menswear and childrenswear.
Over the past five years, the retailer has seen its share of the ВЈ9.9bn value fashion market more than treble.
