(abbreviation for Lan Xang Hom Khao), a feudal Laotian state that lasted from 1353 to 1707 and occupied roughly the territory of present-day Laos and eastern Thailand. In 1545, Lan Xang annexed the principality of Xieng Mai in northwestern Thailand and defeated Siam. From the mid-16th century it led an anti-Burmese coalition of Tai and Laotian states, and between 1570 and 1581 it successfully repulsed several Burmese invasions. Between 1622 and 1637 Lan Xang was embroiled in dynastic struggles and internecine wars, which ended under the ruler Souligna Vongsa (1637–94). He settled the territorial disputes with most of Lan Xang’s neighbors, restored domestic peace, instituted reforms in the official hierarchy, expanded foreign trade relations, and established trade contacts with Holland. Soon after Souligna Vongsa’s death Lan Xang was partitioned into two principalities, Luang Prabang and Vientiane (1707).