For women 10 to 13 % body fat and men 2 to 5 % body fat but even most athletes are above that.
Athletes are usually a few percentage points above that unless they are competing in a sport that requires a low body fat percentage at which point they will reduce their percentage a day or two before.
Both men and women can have up to 10% higher body fat and still be considered 'fit' in fact, your body fat percentage must reach 31% for women and 25% for men before you are considered overweight.