The understanding of congenital naevi has evolved rapidly in the last few years, with the discovery of many of the causative genes, and an increasing understanding of the phenotypic correlates of genotypic mosaicism in the skin. A new classification of all congenital naevi is proposed, based on phenotype, histology and genetics, which allows for the addition of new conditions as they are discovered, and for the regrouping of previously distinct disorders. The clinical features and extracutaneous associations of different congenital naevi are reviewed, as well as those of non‐naevoid developmental abnormalities of the skin.