The manifestation of Lord Vishnu
in tortoise form is called the Kurma Avatar. This is one of the ten incarnations of Lord Vishnu. The deity of Kurma is found in Srikurman which is famous for the Sri Kurmanatha temple.
This architecturally beautiful temple is the only temple devoted to Lord Vishnu's tortoise incarnation. The present temple is at least 700 years old while the original temple is said to have been built in 200 AD.