Aani Uthiram, is dedicated to the Nataraja form of Hindu God Shiva. This Tamil ritual and festival is observed on the Uthram Nakshatram or birth star day in the Aani month. The day is of great significance in Shiva temples all over the world.

Legend has it that on Aani Uthiram day Lord Shiva appeared before Sage Manikkavachakar under a Kurundai Tree and offered upadesha (advice). Sage Manikkavachakar is the author of Thiruvachakam.

Special bathing ritual or Abhishekam is performed on the day on Nataraja Murti or idol at the twilight period (Pradosha period). This ritual is known as Aani Thirumanjam.