Congenital triangular alopecia, also known as temporal triangular alopecia, is a localized patch of alopecia on the frontotemporal scalp. It typically appears within the first 2-9 years of life and very rarely in adulthood. There is no sex predilection, and the disorder is more common in whites and Asians. Familial forms have been reported.

Temporal triangular alopecia presents as loss of hair in a triangular, lancet-shaped, or ovoid pattern on the frontotemporal scalp. The base of the lesion extends to the frontal hairline, while the point, or "tip," of the lesion extends onto the temporal scalp. There is no sharp demarcation between the alopecia and the rest of the scalp. The alopecia is typically unilateral but can be bilateral. A few terminal and/or vellus hairs may be present within the patch of alopecia, or the patch may be completely devoid of hair. However, inflammation and scarring are not present. The size of the lesion remains unchanged throughout life.

There are no known predisposing factors for this variant of alopecia, but case reports of associated conditions include Down syndrome, phakomatosis pigmentovascularis, and seizures.