Mitochondrial DNA (mtDNA) was retrieved for the first time from a Neandertal from the Iberian Peninsula, excavated from the El Sidrón Cave (Asturias, North of Spain), and dated to ca. 43,000 years ago. The sequence suggests that Iberian Neandertals were not genetically distinct from those of other regions. An estimate of effective population size indicates that the genetic history of the Neandertals was not shaped by an extreme population bottleneck associated with the glacial maximum of 130,000 years ago. A high level of polymorphism at sequence position 16258 reflects deeply rooted mtDNA lineages, with the time to the most recent common ancestor at ca. 250,000 years ago. This coincides with the full emergence of the "classical" Neandertal morphology and fits chronologically with a proposed speciation event of Homo neanderthalensis.