A dysplastic nevus or atypical mole is a nevus (mole) whose appearance is different from that of common moles. In 1992, the NIH recommended that the term "dysplastic nevus" be avoided in favor of the term "atypical mole". An atypical mole may also be referred to as an atypical melanocytic nevus, atypical nevus, B-K mole, Clark's nevus, dysplastic melanocytic nevus, or nevus with architectural disorder.

Dysplastic nevi often grow to larger than ordinary moles and may have irregular and indistinct borders. Their color may not be uniform and may range from light pink to very dark brown. They usually begin flat, but parts may be raised above the skin surface. See ABCDE and "ugly duckling" characteristics below.

Dysplastic nevi can be found anywhere, but are most common on the trunk in men, and on the calves in women.

There is some controversy in the dermatology community as to whether or not the "dysplastic"/"atypical" nevus exists. Some have argued that the terms "dysplastic" and "atypical" only refer to diagnostic uncertainty, as opposed to biologic uncertainty, and that the lesion is either a nevus or melanoma from the very beginning, as opposed to some kind of "premalignant stage"; it is only the clinician who is unsure. Some have also argued that even if such nevi do exist, studies have shown that clinicians are unable to reliably identify them anyway, meaning there is no point to even using the concept.