Bangkok is the capital, largest urban area and primary city of Thailand. Known in Thai as Krung Thep Maha Nakhon , meaning "city of angels" for short, it was originally a small trading post on the west bank of the lower Chao Phraya River during the  Ayutthaya Kingdom . It became the capital in 1768 after the destruction of Ayutthaya by Burmese invaders. However, the current Rattanakosin Kingdom did not begin until 1782, when the capital was moved to the east bank of the river by Rama I following the death of King Taksin. The city is more formally called "Phra Nakhon", referring to the original boundaries of the 18th century, while the name Krungthep Mahanakorn includes the urban areas which have since grown. Foreigners generally call the city by its original name of Bangkok.

The Bangkok special administrative area covers 1,568.7 km 2 (606 sq mi), making it the 68th largest province in Thailand. Much of the area is considered the city of Bangkok, therefore making it one of the largest cities in the world. The Chao Phraya River, which stretches 372 km (231 mi), is Bangkok's main geographical feature. The Chao Phraya River basin, the area surrounding Bangkok, and the nearby provinces comprise a series of plains and river deltas that lead into the Bay of Bangkok about 30 km (19 mi) south of the city center. This gave rise to Bangkok's appellation as the " Venice of the East" due to the number of canals and passages that divide the area into separate patches of land. The city once used these canals, which were plentiful within Bangkok itself, as divisions for city districts. However, as the city grew in the second half of the 20th century, the plan was abandoned and a different system of division was adopted.

The town of Bangkok began as a small trading center and port community on the west bank of the Chao Phraya River before the establishment of the Ayutthaya Kingdom , the precursor of modern Thailand, which existed from 1350 to 1767. The etymology of the town's name is unclear. Bang is the Central Thai name for a town situated on the bank of a river. It is believed that "Bangkok" derived from either Bangkok, kok being the Thai name for the Java plum ( ma-kok ), one of several trees bearing olive-like fruits); or Bang Koh , koh   meaning "island," a reference to the area's landscape which was carved by rivers and canals. After the fall of Ayutthaya to the Burmese Kingdom  in 1767, the newly declared King Taksin established a new capital in the area of the then Bangkok, which became known as Thonburi . When Taksin's reign ended in 1782, King Buddha Yodfa Chulaloke   reconstructed the capital on the east bank of the river and gave the city a ceremonial name which became shortened to its current official name,   Krung Thep Maha Nakhon . The new city, however, also inherited the name Bangkok, which continued to be used by foreigners to refer to the entire city and became its official English name, while in Thai the name still refers only to the old district on the west bank of the river. The city has since vastly modernized and undergone numerous changes, including the introduction of transportation and utility infrastructure in the reigns of King Mongkut and King Chulalongkorn, and quickly developed into the economic center of Thailand.