Udayagiri Fort, Military fort in Padmanabhapuram, India.

Udayagiri Fort is a granite fortification encircling an isolated 260-foot hillock on about 90 acres at Puliyoorkurichi, 14 km from Nagercoil. Its walls of massive granite blocks enclose a partly ruined chapel, an old gun foundry and a tunnel found by Archaeology Department officials. The site now lies within a biodiversity park of the Tamil Nadu forest department.

The Maharaja of Travancore rebuilt the fort between 1741 and 1744 with help from Dutch commander Eustachius De Lannoy. This reconstruction transformed it into a significant military installation in the region.

The chapel inside holds the graves of Dutch commander De Lannoy and his family, marked with inscriptions in both Tamil and Latin. These tombs show how European and local traditions came together at this place.

The fort lies 14 km from Nagercoil on the Thiruvananthapuram–Nagercoil national highway at Puliyoorkurichi, near Thuckalay. It is now a biodiversity park run by the Tamil Nadu forest department, with a fenced deer area, bird and guinea pig cages, and a small aquarium. Entry is allowed to families and to men or women visiting alone; male–female couples and mixed groups of friends are refused. Separate charges apply for the Burma bridge walk and the tree hut climb.

The fort once housed a foundry where cannons, mortars, and cannonballs were manufactured on site. This production capability shows how technologically advanced the installation was for its era.