Even in the jet-set crowd at the Paris fashion shows, Giambattista Valli's front row stood out last week. It was lined with European socialites, from Greek shipping heiress Eugenie Niarchos to Russian oligarch Alexander Lebedev and his son Evgeny.

In the six years since he launched his own fashion house, Mr. Valli has become a go-to designer for the rich and royal. Producing confections of silk satin, cashmere and tulle that have been compared to Rolls-Royce sedans and have prices to match, he has dressed clients from Queen Rania of Jordan to Sarah Jessica Parker.