King Setthathirath (Lao: ເສດຖາທິຣາດ; 1534–1571) or Xaysettha (Lao: ໄຊເສດຖາ; Thai: ไชยเชษฐาธิราช Chaiyachetthathirat) is considered one of the great leaders in Lao history. Throughout the 1560s until his death, he successfully defended his kingdom of Lan Xang against military campaigns of Burmese conqueror Bayinnaung, who had already subdued Xieng Mai (Chiang Mai) in 1558 and Ayutthaya in 1564. Setthathirath was a prolific builder and erected many Buddhist monuments including Wat Xieng Thong in Louang Phrabang and the That Luang in Viangchan.
Setthathirath also known as Chaiyachettha or Chaiyaset or Jayajestha, Son of the King Photisarath of Lan Xang, he was crowned King of Lanna after the death of his grandfather, Ketklao the previous King of Lanna, who died without a male heir to the throne and gave his daughter Princess Yotkhamtip in marriage to his father King Photisarath of Lan Xang.
After the death of King Photisararath, the nobles of Lan Xang were divided, a group supported Prince Tha Heua, another group of nobles led by Phya Vieng, Saen Marong and Kwan Darmpa supported Prince Lanchang who was born from an Ayutthayan princess. Prince Tha Heua and Prince Lanchang began to split the Kingdom up between them, when Prince Settathathirath was still in Chiang Mai. Hearing of the news of his half brothers, King Settathathirath quickly returned to Lan Xang leaving the affairs of Chiang Mai under Queen Chiraprapha's leadership, taking with him the Phra Kaew (Emerald Buddha), the Saekkam and the Sihing buddha images.
In 1572, a conspiracy between Lord Phya Nakhon and the former abbot of Wat Maximavat, who held personal grudges against Setthathirath, led to the king's murder in the southern frontier of the country. He was 38 years of age.