Chattagahaka Jantu (a.k.a. Chhattagahaka) was king of Anuradhapura for about one year from 434 AD to 435 AD. He succeeded his wife's stepbrother Soththisena and was succeeded by Mittasena.
He was from the House of Lambakanna I. Prince Jantu had the office of Chattagahaka before he became king. He was the husband of Princess Sanghā, the daughter of King Mahānāma (410-432).Reflections on a Heritage: Historical Scholarship on Premodern Sri Lanka p 132 He succeeded his wife's step brother Soththisena as the king of Anuradhapura. He was succeeded by Mittasena. The Chief Minister wanted to ascend the throne himself, but enthroned Mittasena as his puppet ruler.
See also List of Sri Lankan monarchs History of Sri Lanka
References
Kings & Rulers of Sri Lanka Codrington's Short History of Ceylon