Ketheeswaram temple is an ancient Hindu temple in Mannar, Northern Province, Sri Lanka. It is the oldest temple in Sri Lanka with at least 1400 years of evidence. Overlooking the ancient Tamil port towns of Manthai and Kudiramalai, the temple has lain in ruins, been restored, renovated and enlarged by various royals and devotees throughout its history. Thirukketheeswaram is one of the Pancha Ishwarams dedicated to the Hindu deity Shiva and is venerated by Shaivas throughout the continent. Throughout its history, the temple has been administered and frequented by Sri Lankan Hindu Tamils. Its famous tank, the Palavi tank, is of ancient antiquity and was restored from the ruins. Thirukketheeswaram is one of the 275 Paadal Petra Sthalams of Shiva glorified in the poems of the Tevaram.

Mannar is the main town of Mannar District, Northern Province, Sri Lanka. It is governed by an Urban Council. The town is located on Mannar Island overlooking the Gulf of Mannar and is home to the historic Ketheeswaram temple. In the Tamil language, Mannar means the raised place [of sand] which is thought to have come from the geology of Mannar Island which was formed by the accumulation of sand.