Mythological and historical sketches of the Sri Lankan population indicate that it is heterogeneous and composed of diverse ethnic groups. Ancient chronicles of Sri Lanka relate the origin of the Sinhalese to the legend of Prince Vijaya, who arrived on the northwest coast of the island in 543 B.C. from northeast or northwest India. Further, because Sri Lanka occupies an important position on seaways, it has received a constant influx of people from various parts of the world (especially from the Middle East and Europe), including India. Taking into consideration mythological, historical, and linguistic records of Sri Lanka, I attempt to study the degree of gene diversity and genetic admixture among the population groups of Sri Lanka along with the populations of southern, northeastern, and northwestern India, the Middle East, and Europe. The genetic distance analysis was conducted using 43 alleles controlled by 15 codominant loci in 8 populations and 40 alleles controlled by 13 codominant loci in 11 populations. Both analyses give a similar picture, indicating that present-day Sinhalese and Tamils of Sri Lanka are closer to Indian Tamils and South Indian Muslims. They are farthest from Veddahs and quite distant from Gujaratis and Punjabis of northwest India and Bengalis of northeast India. Veddahs are distinct because they are confined to inhospitable dry zones and are hardly influenced by their neighbors. The study of genetic admixture revealed that the Sinhalese of Sri Lanka have a higher contribution from the Tamils of southern India (69.86% +/- 0.61) compared with the Bengalis of northeast India (25.41% +/- 0.51), whereas the Tamils of Sri Lanka have received a higher contribution from the Sinhalese of Sri Lanka (55.20% +/- 9.47) compared with the Tamils of India (16.63% +/- 8.73). Thus it is apparent that the contribution of Prince Vijaya and his companions, coming from northwest India, to the present-day Sinhalese must have been erased by the long-standing contribution (over 2000 years) of the population groups of India, especially those from Bengal and Tamil Nadu. Similarly, the Tamils of Sri Lanka are closer to the Sinhalese because they were always in close proximity to each other historically, linguistically, and culturally.