The fashion designer who reportedly had a relationship with Winston Churchill was Coco Chanel. It's been rumored that the two had a romantic relationship that lasted for several years, although the exact nature of their relationship is not entirely clear. Some sources suggest that Churchill was infatuated with Chanel, while others claim that they were simply close friends. Regardless of the exact nature of their relationship, it's fairly well-established that the two had a deep mutual respect for each other, and that Chanel was one of Churchill's favorite fashion designers.