{ { Infobox monarch
| name =Setthathirathເສດຖາທິຣາຊ
| title =King of Lan Xang King of Lan Na
| image =Setthathirat.JPG
| caption =Statue of King SetthathirathPha That Luang, Vientiane
| succession =
| reign =1548-1571
| predecessor =Photisarath I
| successor =Sen Soulintha
| coronation =1550
| succession1 =
| predecessor1 =Chiraprapha
| successor1 =Mekuti
| reign1 =1546-1551
| coronation1 =1546
| spouse =
Ton Thip of Lan NaTon Kham of Lan NaThepkasattri of AyutthayaKaew Pra Kham, daughter of Sen Soulintha | issue = Prince Nokaeo KoumanePrincess Khau PhengOther Princesses | dynasty =Khun Lo | father =Photisarath I | mother =Yotkhamthip of Lan Na | religion =Therevada Buddhism | birth_name =Setthavangso | birth_date =24 January 1534 | birth_place =Muang Sua, Lan Xang | death_date =1571 | death_place =Attapeu, Lan Xang | date of burial = | place of burial = | regnal name = Samdach Brhat-Anya Chao Udaya Budhara Bhuwana Brhat Jaya Jettha Maharajadhiraja Bhuwanadya Adhipati Sri Sadhana Ganayudha|}} Setthathirath (; 24 January 1534 – 1571) or Xaysettha (; , , ) 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 Luang Prabang, Haw Phra Kaew, Wat Ong Teu Mahawihan and the Pha That Luang in Vientiane.
King of Lanna
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.
When King Ketklao died, there was no other descendant available to succeed him. High-ranking officials and Buddhist monks therefore agreed unanimously to assign the Lanna throne to Prince Setthathirath in 1546. His name was lengthened to Chao Chaiyasetthathirath.
In 1548 King Setthathirath (as King of Lanna) had taken Chiang Saen as his capital. Chiang Mai still had powerful factions at court, and the threats from Burma and Ayutthaya were growing.
King 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 Phra Phuttha Sihing images. He also claimed that taking the statue would allow his relatives the opportunity to venerate the image and make merit. The Nobles of Lanna felt that Setthathirath had stayed away too long, and sought another descendant of Mangrai dynasty to take the throne in 1551. They chose a distant relative of Setthathirath, the Shan Prince known as Mekuti.
Settathathirath subdued Prince Tarua in Louang Phrabang, and sent his general Phya Sisatthamatailoke to go fight Prince Lanchang in the town of Kengsah, Prince Lanchang was defeated and fled to Thakhek, where the local Lord had him arrested and sent to Phya Sisatthama. The nobles that supported Prince Lanchang were executed, but Prince Setthatathirath pardoned Prince Lanchang and appointed him as governor of Seanmuang. Phya Sisatthama was thus made Lord of Viangchan, and given the title Phya Chantaburi, who built Wat Chan and Pia Wat that can be still found in Viangchan today.
In 1553 King Setthathirath sent an army to retake Lanna from Mekuti but was defeated. Again in 1555 King Setthathirath sent an army to retake Lanna at the command of Sen Soulintha, and managed to take Chiang Saen. For his success, Sen Soulintha was given the title Luxai (Victorious) and offered one of his daughters to King Setthathirath. In 1556 Burma, under King Bayinnaung invaded Lanna. King Mekuti of Lanna surrendered Chiang Mai without a fight, but was reinstated as a Burmese vassal under military occupation.