Koothanallur is a city and a municipality in Thiruvarur district in the Indian state of Tamil Nadu.

Koothanallur, a small village started from the Turkish colonization, Koothanallur derives its name from two cultivator-brothers called Younger Koothan and Elder Koothan who are believed to have been the original settlers in the patch of wet lands some 800 years ago. "Nallur" denotes the welfare status of the village those days. The present Koothanallur is a municipal town of 12.31 square kilometres in area, lying on the route between Mannargudi and Tiruvarur of old East Tanjore District, some 350 kilometres south east of Chennai. It is populated predominantly by Muslim community. River Vennar, which flows through the heart of the town, keeps the soil most fertile. The history began when Turkish traders and missionaries settled in Koothanallur and build a first mosque in Big Street in 12th century.

The residents of Koothanallur, Podakkudi and Attikadai were very well known for their cleanliness and beauty because they were the descendent of Sultanate of Rum (Rome). Koothanallur ancestors known came from Turkey, Greek, Albania and Arab Bedouin, none of them was known converted from Hindu to Islam. Most of them had fair complexion but the dark complexion ones was the Bedouin generation. A written rock in Turkish language was found at the wall of Chinnapalli and Big Mosque.