Marc Jacobs -- Hurricane Sandy DESTROYED My Apartment

Designer Marc Jacobs was among the hardest hit by Hurricane Sandy last weekend -- telling TMZ, he completely lost his Manhattan apartment due to flooding ... and now, he's looking for a new place to live.

Marc was out walking his dog Friday in New York -- and he told us, he had to move uptown temporarily because Sandy completely destroyed his West Village apartment.

Marc says it's so bad, he hasn't even been able to go back to try to salvage some of his belongings.