The 44-year-old Belgian replaces John Galliano, who left in disgrace last year after.
The Paris-based fashion house believes that Simons will “inspire and push into the 21st Century” the Dior style.
Raf Simons, who previously designed for the Jil Sander label, will present his first show for Dior in July.
Mr Galliano was sacked last year after being filmed in a Paris bar using anti-Semitic insults.
He was convicted and fined by a French court. The British designer blamed drug and alcohol addictions for the outburst. Mr Galliano’s former assistant Bill Gaytten has overseen Dior’s collections since he left.
