Karthigai Deepam is a regional name for the Indian festival known as Deepavali or Diwali. It is essentially the festival of lights. This festival of light is celebrated in the Kaarthigai month (a Tamil month). Karthigai Deepam is observed on the day of full moon. Being one of the forms of the festival of Diwali, it is celebrated the same way as diwali. On this festival many houses kindle traditional lamps and spread light everywhere.

Karthigai Deepam is also popularly known as Annamalai Deepam. According to one legend this festival is celebrated on the context of finding the head and feet of Lord Shiva. It is believed that Lord Shiva once asked Lord Brahma and Lord Vishnu to find out the accurate location of his head and feet. However, the larger than life form of Lord Shiva made it impossible for both the deities to locate these organs. In order to help the lords of the lords Brahma and Vishnu, Lord Shiva incarnated the form of jyoti (light of fire) on the hill of Thiruvannamali and marked the birth of this festival.

And it is with this belief that Annamalai Deepam or the Karthigai Deepam is celebrated in a special manner in Thiruvannamalai. Every year in Thiruvannamalai a special torch is lighted on the peak of the hill with a staunch belief that Lord Shiva's jyoti will one day be visible to the naked eyes.

On Karthigai Deepam special pujas are offered to Lord Muruga also who is believed to have taken the form of six babies in a lake called "Saravana Poigai".

This festival of lights lasts for three days. It is celebrated in a very colorful manner. People clean their houses, draw rangoli or kolams in their yards and put lamps on it.