Karainagar (Tamil: காரை நகர்) (pronounced Kaarai-Nagar) is located 20 km from Jaffna, Sri Lanka, on the Karaitivu (Island). In Tamil, means a place with abundant Kaarai trees. However, the word Karai also means the coast, as derived from the Tamil word 'kadar-karai' meaning a settlement (or town) on the sea coast (kadar or kadal means sea and karai means coast) which is borne by the fact that Karainagar is a coastal town.

Karainagar island is about 10-square-mile (26 km2) area and the registered voters 20,000 voted in 1977 national election. The current population stands at 11,000. 30% of this land is used for paddy cultivation.