Karthikai Deepam (Tamil: திருகார்த்திகை தீபம் / கார்த்திகை விளக்கீடு, Malayalam: തൃക്കാർത്തിക / കാർത്തിക വിളക്ക്), also spelled Karthigai Deepam or Karthika Deepam is one of the most ancient festivals that has been celebrated since ages according to Indian history. It is symbolic of the festival of lights in Tamil Nadu, Kerala and some regions of Andhra Pradesh and is dedicated to the infiniteness of The Almighty.

The most ancient mythology associated with this festival is when Lord Brahma and Lord Vishnu once started quarrelling with each other over their individual supremacy in terms of power and strength. Distressed by their arguments, Lord Shiva emerged in front of them as a flame of fire. Lord Brahma and Vishnu decided to compete with each other to find the start and end of this flame. For this Brahma took the form of a swan and Vishnu took the form of a boar. Finally when none of them won, Lord Shiva emerged back into form and thus emphasized about the infiniteness and ultimate existence of God that is beyond all measurements.

Lord Muruga took the form of six flames that emerged from the eyes of Lord Shiva. These flames took the form of six babies and accumulated in a lake known as 'Saravana Poigai'. On this day, these nymphs were accumulated by Goddess Parvati and thereafter Karthikai Deepam is also the day when Lord Muruga is worshipped.