The 65-year-old Olympian was previously known as Bruce Jenner before her gender transition earlier this year and Marc is proud of Caitlyn for becoming ''who she was born to be''.
Designer Marc told the French edition of Glamour magazine: ''She's an incredible woman very brave, which is actually quite paradoxical if you think about it because we wouldn't call her brave if society as we know it was less afraid of what makes people different. She wasn't happy in her body so she just became who she was born to be.''
Marc was also keen to make the point that Caitlyn's experience as a transgender person is different from transvestites, who simply like to dress in clothing of the opposite sex.
He explained: ''Wearing woman's clothes and feeling you are a woman are two different things. I know a lot of drag-queens who have no desire to change sex. I have been wearing skirts and dresses for a very long time, I'm not a transvestite but I wear what I want and I don't care. For example, Prada designed a fur coat for me, I just asked them to sew the buttons on the other side. A coat is a coat at the end of the day. I don't need to know people's religion, their jobs, their sexual identity. I'd like to quote RuPaul here, 'We're all born naked, the rest is drag.' ''