The first store launches on 12 November in the Birmingham Bullring followed the next day by the launch of a site at Dublin's Jervis Centre along with an online presence through forever21.com.
A further store is expected at London's Westfield shopping centre in Stratford, which is currently under construction.
Linda Chang, senior marketing manager at Forever 21, said: "Amber Le Bon is the perfect model for our launch into the UK.
"Her fresh young look truly embodies the Forever 21 brand and exemplifies our blend of fun, fast-fashion and trend setting apparel and accessories."
Le Bon said: "Whenever I’m in the US I always make time to visit their stores and I know how excited fashion fans in the UK are to have Forever 21 coming here."
Forever 21 stock lines for women, men and children. The chain already has stores in continental Europe, the Middle East, Asia Pacific and the US.
It was founded in Los Angeles in 1984 as Fashion 21. In the UK it is set to compete against the likes of Urban Outfitters H&M, Gap, Mango and New Look.
Le Bon is the daughter of Duran Duran frontman Simon Le Bon and fashion model Yasmin Le Bon. She has modelled for brands including Moschino and River Island and is currently the face of Myla swimwear and fronts a campaign for shampoo brand Pantene.