Kattankudy or Kattankudi is a small city in Eastern province of Sri Lanka, notable for being one of the most densely populated cities in South Asia and the most densely populated Muslim region in the world. It was the site of the Kattankudy mosque massacre of 1990.

With over 40,000 inhabitants, Kattankudi is one of the few cities in Sri Lanka where ethnic Moors (Muslims) form the over all majority of the population. It is also the city with the most number of mosques per square kilometer in the world. Villages and towns surrounding the city, however are dominated by Tamils; hence ethnic conflicts between the two communities are common. In several occasions, the city has been a hotspot for fighting between the Sri Lankan government and the Liberation Tigers of Tamil Eelam (LTTE).