Madam Malkin's

Though far from the only wizarding clothier around, Madam Malkin's seems to be the best, as it is the place where most Hogwarts students purchase their robes. Madam Malkin's is located next door to Flourish & Blotts, and in addition to selling Hogwarts school robes, they also sell robes which are "spangled, self-ironing, beautifying, slimming, fattening, lengthening," and "temperature-adjusting".