Kári Stefánsson is an Icelandic neurologist and founder and CEO of Reykjavik-based biopharmaceutical company deCODE genetics. In Iceland he has pioneered the use of population-scale genetics to understand variation in the sequence of the human genome. His work has focused on how genomic diversity is generated and on the discovery of sequence variants impacting susceptibility to common diseases. This population approach has served as a model for national genome projects around the world and contributed to the realization of several aspects of precision medicine.