Modern taxonomy relies on the unified species concept and integrative approaches to delimit evolutionary coherent taxa. The western Mediterranean vipers within the Vipera latastei–monticola complex (Vipera latastei and Vipera monticola) have a rather old taxonomic history marked by the prevalence of morphological criteria in the recognition of taxonomic units. Recent phylogenetic inferences, however, contradict this taxonomic scenario, highlighting the need of integrative studies to properly evaluate the taxonomy of this complex. Here, we apply an integrative taxonomic approach, combining phylogeographic, morphological, and ecological analyses, to identify and describe evolutionary coherent taxonomic units within the Vipera latastei–monticola complex. Using dated mtDNA phylogenetic relationships, we spatially delimit two levels of evolutionary units, which are the subject of morphological and ecological comparisons. The first level corresponds to two Miocene vicariant clades, with considerable morphological distinctiveness that we identified as different species: V. latastei in the Iberian Peninsula, and V. monticola in North Africa. The second level corresponds to three Pliocene parapatric lineages within each of these species, which we recognized with subspecific status due to non-apparent geographic isolation and variable levels of phenotypic distinctiveness. Consequently, we propose distributional rearrangements in the previously recognized taxa, as well as define three new subspecies: Vipera latastei arundana ssp. nov. in southern Iberia, Vipera monticola atlantica ssp. nov. in the western High Atlas Mountains and Vipera monticola saintgironsi ssp. nov. in the eastern High Atlas, Middle Atlas, Rif, Tellian Atlas and Aurès Mountains. Our proposed taxonomic scenario anticipates important outcomes for the conservation status of these Mediterranean taxa. La taxonomía moderna se basa en el concepto de especie unificada y en enfoques integrativos para delimitar taxones evolutivos coherentes. Las víboras del Mediterráneo occidental incluidas en el complejo Vipera latastei-monticola (Vipera latastei y Vipera monticola) tienen una historia taxonómica bastante antigua, marcada por la prevalencia de criterios morfológicos en el reconocimiento de unidades taxonómicas. Sin embargo, recientes inferencias filogenéticas contradicen este escenario taxonómico, destacando la necesidad de estudios integrativos para evaluar adecuadamente la taxonomía de este complejo. Aquí aplicamos un enfoque taxonómico integrativo, combinando análisis filogeográficos, morfológicos y ecológicos, para identificar y describir unidades taxonómicas evolutivas coherentes dentro del complejo Vipera latastei-monticola. Utilizando relaciones filogenéticas datadas basadas en ADN mitocondrial, delimitamos espacialmente dos niveles de unidades evolutivas, que son objeto de comparaciones morfológicas y ecológicas. El primer nivel corresponde a dos clados vicariantes del Mioceno, con una marcada distinción morfológica y que identificamos como especies diferentes: V. latastei en la Península Ibérica y V. monticola en el norte de África. El segundo nivel corresponde a tres linajes parapátricos del Plioceno dentro de cada una de estas especies, que identificamos con nivel subespecífico debido a una aparente falta de aislamiento geográfico y niveles variables de diferenciación fenotípica. Consecuentemente, proponemos cambios en los rangos de distribución de los taxones previamente reconocidos, y definimos tres nuevas subespecies: Vipera latastei arundana ssp. nov. en el sur de Iberia, Vipera monticola atlantica ssp. nov. en las montañas del Alto Atlas occidental y Vipera monticola saintgironsi ssp. nov. en el este del Alto Atlas, Medio Atlas, Rif, Atlas Teliano y montañas de Aurès. Nuestro escenario taxonómico propuesto anticipa resultados importantes para el estado de conservación de estos taxones mediterráneos. Figure S1. Distribution of samples used for mtDNA phylogenetic analyses. Figure S2. Distribution of measured animals considered for morphological analyses. Figure S3. Distribution of occurrences considered for ecological analyses. Figure S4. Dated mtDNA phylogenetic tree and distribution map showing the location of new samples considered in this work. Figure S5. Lineages delimitation and distribution of occurrences. Table S1. List of sequences used in this study. Table S2. Number of individuals considered for morphological analyses. Table S3. Number of specimens considered according to sex. Table S4. Uncorrected distances in cytb gene among clades and lineages. Table S5. Descriptive statistics of morphological traits for the comparison between Vipera latastei and Vipera monticola. Table S6. Descriptive statistics of morphological traits for Vipera latastei subspecies. Table S7. Descriptive statistics of morphological traits for Vipera monticola subspecies. Table S8. Descriptive statistics for the topo-climatic variables defining ecological niches of Vipera latastei and Vipera monticola. Table S9. Descriptive statistics for the topo-climatic variables defining ecological niches of Vipera latastei latastei, Vipera latastei gaditana and Vipera latastei arundana ssp. nov. Table S10. Descriptive statistics for the topo-climatic variables defining ecological niches of Vipera monticola monticola, Vipera monticola atlantica ssp. nov. and Vipera monticola saintgironsi ssp. nov Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.