Chaliang (Thai: เชลียง, Chinese: 程良) or Sawankhalok, later known as Si Satchanalai, was a political entity in the upper Chao Phraya Valley in central Thailand. It was founded in the early 600s by uniting four regional chiefdoms, with Haritvanlee or Chaliang (นครหริตวัลลีย์) as the center, and became part of the Dvaravati's Lavo. In 1001, Chaliang was referred to as an independent kingdom Chéng Liáng in the Chinese text Song Shi. The term San-lo (三濼) mentioned in Lingwai Daida in 1178 plausibly referred to Chaliang's new center, Sawankhalok.

After Haripuñjaya and Suphannabhum reclaimed Lavo from Angkor in 1052, Lavo's king, Phra Narai, moved the capital to Ayodhya in the 1080s and left the throne at Lavapura. The Mon-Tai dynasty of Chaliang took over and moved the seat southward to Lavo's former capital Lavapura; Chaliang then again became Lavapura's northern fortress. However, this dynasty later lost Lavapura to Angkor following the Angkorian influence-expanding campaign to the Menam Valley in 1181. During this era, this Mon-Tai dynasty also established royal intermarriages with the Siamese (Xiān) at Ayodhya. Their descendants, later known as the Uthong (Lavo) dynasty, continued to rule Ayodhya until the traditional formation of the Ayutthaya Kingdom in 1351.

In 1157/58, Chaliang was occupied by another Tai monarch from Chawa (ชวา, Muang Sua) or Nam Ou basin. This monarch, led by Sri Naw Nam Thum, expanded political influence to Sukhothai of Lavo in 1175. However, nobles of the Lavo faction revolted and recaptured Sukhothai in 1181, which caused Tai kings from Mueang Rad and Mueang Bang Yang to join forces and retake Sukhothai in 1238. This marked the formation of the Sukhothai Kingdom.

During the Sukhothai era, Chaliang was comparable and equal to Sukhothai, in which both cities were the capitals. However, after the Sukhothai Kingdom became the vassal of Ayutthaya, Chaliang lost its political influence and was later demoted to the frontier city after Ayutthaya lost it to Lan Na in the 15th century.

The English term "Chaliang" is the romanization of the Thai word "เชลียง" per the Royal Thai General System of Transcription. The Thai word for the historical country was plausible a transliteration of the combination of two words: the Sanskrit word Chala (Sanskrit: जल) which means "water" and the Old Mon word Wang which means "city". Together, the combined word can be interpreted as meaning "city of water," as the city is almost surrounded by the Yom River.

The region was inhabited since the Neolithic–Iron Ages. It then evolved into agricultural communities in the early 4th century and turned into complex societies around the 9th century. Artifacts found in Chaliang-Si Satchanalai show that the communities engaged in trade with several Dvaravati polities, such as Si Mahosot [th] in the southeast, and Mueang Fa Daet Song Yang and Ban Mueang Fai (บ้านเมืองฝ้าย) in northeastern Thailand. Chaliang, on the great bend of the Yom River, was likely inhabited by Mon people who had migrated from the lower Chao Phraya basin, whereas Si Satchanalai, which was situated close to the base of the mountain and along the river, was probably of the people from the northern highlands, the Tais.

According to the Northern Chronicle [th], Chaliang was founded in the early 600s by a hermit, Satchanalai (สัชนาลัย; or Anusit อนุสิสส in the Tamnan Mulasasana [th]), who united four surrounding chiefdoms and built moats and walls to define the city's boundaries. Chaliang layout is also the model for Haripuñjaya's plan, which Hermit Suthep built, indicating that it existed before Haripuñjaya's establishment in 629. In the first era, Chaliang's initial territory included Thung Yung [th] or Wiang Chao Ngo [th] to the northeast and met Sukhothai to the south.

Hermit Satchanalai had four colleagues, each of whom played an important role in the establishment of the ancient kingdoms in modern-day Thailand, as detailed below.