|Cities||Nan, Uttaradit, Phitsanulok, Phichit, Nakhon Sawan|
|• location||Luang Prabang Range, Bo Kluea District, Nan Province|
|• coordinates||19°20′0″N101°12′0″E / 19.33333°N 101.20000°E|
|• elevation||1,240 m (4,070 ft)|
|Mouth||Confluence with Ping River|
|Pak Nam Pho, Nakhon Sawan Province|
|25 m (82 ft)|
|Length||740 km (460 mi) |
|Basin size||57,947 km2 (22,373 sq mi)|
|• location||Nakhon Sawan |
|• average||472 m3/s (16,700 cu ft/s)|
|• maximum||1,522 m3/s (53,700 cu ft/s)|
|• left||Lam Wa, Nam Pat, Khwae Noi River, Wang Thong River|
|• right||Yom River|
The Nan River (Thai : แม่น้ำน่าน, RTGS: Maenam Nan, pronounced [mɛ̂ː.náːm nâːn] ) is a river in Thailand. It is one of the most important tributaries of the Chao Phraya River.
The Nan River originates in the Luang Prabang Range, Nan Province. The provinces along the river after Nan Province are Uttaradit, Phitsanulok and Phichit. The Yom River joins the Nan River at Chum Saeng District, Nakhon Sawan Province. When the Nan river joins together with the Ping River at Pak Nam Pho within the town Nakhon Sawan it becomes the Chao Phraya River. The Nan river runs about 630 kilometres (390 mi) south.
The chief tributary of the Nan is the Yom River, which joins the Nan within Chum Saeng District in Nakhon Sawan Province. Other direct tributaries include Khlong Butsabong and Khlong San Thao of the lower Nan Basin, the Wat Ta Yom and Wang Thong Rivers which join the Nan within Phichit Province, the Khwae Noi River which joins the Nan within Phitsanulok Province, Khlong Tron and Nam Pat, which join the Nan within Uttaradit Province, Lam Wa, Nam Haet, Nam Pua, Nam Yao and Nam Hao, which join the Nan within Nan Province.
Kaeng Luang is a waterfall on the Nan River in Nan Province. 
The expanse of the Nan River's tributaries, i.e. the Nan River System, together with the land upon which falling rain drains into these bodies of water, form the Greater Nan Drainage Basin, which is part of the Chao Phraya watershed.  The total area drained by the Nan and its tributaries is 57,947 square kilometres (22,373 sq mi). Much of the lower basin has perfect soil for farming.
Most drainage analyses, however, divide the Greater Nan Basin into the Nan Basin and the Yom River Basin. Using this convention, and subtracting the 23,616 square kilometres (9,118 sq mi) of land drained by the Yom and its tributaries, the Nan basin drains a total of 34,331 square kilometres (13,255 sq mi) of land in the provinces of Phitsanulok, Phichit, Nan and Uttaradit.
Ancient civilizations lived in the fertile land along the Nan River and its tributaries, as is evidenced by Stone Age tools unearthed near Phitsanulok. However, these early hunter-gatherers are not likely to be ancestors of the Tai who presently inhabit the Nan basin. The human population around the Chao Phraya River and its tributaries, such as the Nan, remained sparse until late in the region’s history.  The settlement of the indigenous populations of the region began around the advent of rice agriculture during the Bronze Age, and continued through the Iron Age.  Archaeologists suspect that Mon–Khmer speaking tribes spread through the region, bringing rice agriculture, metalworking, domestic animals. The main course of migration during the metal ages probably ran along the coast of Thailand, but migrants also travelled inland along the Chao Phraya to the Nan Basin and other areas, where it was relatively easier to establish settlements.  The next major wave of migration into the Nan Basin came not from the coast along the Chao Phraya, but rather from the mountainous areas of northern Thailand.  These migrants were the Tai.  Their course of immigration probably began south of the Yangzi River.  As the Han Chinese spread south of the Yangzi around the sixth century BC, the ancestors of the Thai retreated into the high valleys and, over many centuries, migrated west along an arc from the Guangxi to the Brahmaputra Valley. The Thai brought rice-farming expertise to the mountainous areas of Northern Thailand, and eventually to the Nan Basin and the other lowland regions of Thailand.  Some of the Nan River Mon-Khmer retreated into the hills as the Thai expansion continued, while others generally adopted dialects of the Tai language and blended into the culture of the new settlers.  The Tai language spoken in the area was heavily influenced by the Khmer culture as well, and evolved into the language we now call Thai, which is considerably different from other Tai dialects.  Even after this Thai migration, the population in the Nan Basin, other than along the banks of the Nan River and its major tributaries, was sparse.  predator animal species, as well as malaria, tropical temperatures and other hardships, kept the population from expanding far from the river, despite the region's extremely fertile soil.  As the population grew during these ancient times, settlements along the Nan eventually became more urban, as populations of larger scale were better able to survive the hardships of the heavily forested region. The earliest urban developments along the Nan were modelled after the Mon-Khmer capital at Angkor in Cambodia, which was already quite advanced by the time the Nan Basin had significant population to support urban settlement.  Along with the positive effects of urbanization (e.g., development of art and specialization of labor), however, came slavery, war and other societal problems associated with urban culture in the forecoming city-state period.  Even in spite of urbanization along the river banks, most of the Nan Basin (aside from the river-side settlements) consisted of virgin forests until around the turn of the 20th century.  One of the early river-side urban areas of the Nan emerging during the era of the Khmer Empire was Song Khwae, which over the years developed into the modern city of Phitsanulok.
Phitsanulok is the only place in Thailand where houseboats are legal, as they have been an important aspect of regional culture since long before the drafting of modern municipal law. People of Phitsanulok still gather on houseboats and raft houses along both sides of the Nan River in the city, and adhere to a traditional way of life.  There is even a floating houseboat museum along the Nan in Phitsanulok, which allows tourists to experience the Nan houseboat culture first-hand.
The Naresuan Dam, named after King Naresuan, was constructed throughout the span of 1976 through 1985 on the Nan River in Phitsanulok Province, north of the city of Phitsanulok, as part of the Phitsanulok Irrigation Project. 
Water quality in the Nan River is deteriorating from heavy bacterial contamination attributed primarily to the rapid increase of urban development in the provinces of Phitsanulok, Phichit, Nan and Uttaradit. 
The Chao Phraya is the major river in Thailand, with its low alluvial plain forming the centre of the country. It flows through Bangkok and then into the Gulf of Thailand.
Northern Thailand, or more specifically Lanna, is geographically characterised by several mountain ranges, which continue from the Shan Hills in bordering Myanmar to Laos, and the river valleys which cut through them. Though like most of Thailand, it has a tropical savanna climate, its relatively high elevation and latitude contribute to more pronounced seasonal temperature variation, with cooler winters than the other regions. Historically it is related to the Lanna Kingdom and its culture.
The Yom River is a river in Thailand. It is the main tributary of the Nan River. The Yom River has its source in the Phi Pan Nam Range in Pong District, Phayao Province. Leaving Phayao, it flows through Phrae and Sukhothai as the main water resource of both provinces before it joins the Nan River at Chum Saeng District, Nakhon Sawan Province.
The Sakae Krang River is a tributary of the Chao Phraya River. It originates in Mae Wong National Park, Nakhon Sawan Province. It is 225 kilometres (140 mi) long, with most of its length in Uthai Thani Province. It joins the Chao Phraya River in Uthai Thani city near the Wat Tha Sung.
Chat Trakan is the northernmost district (amphoe) of Phitsanulok province, central Thailand.
Phrom Phiram is a district (amphoe) in the northwestern part of Phitsanulok province, central Thailand. The district name means "the beautiful city of Brahma".
Bang Rakam is a district (amphoe) in the western part of Phitsanulok province, central Thailand.
Wang Thong is a district (amphoe) of Phitsanulok province, central Thailand.
The Wang Thong River is a river in Thailand. Its source lies in the Phetchabun Mountains in the Khao Kho District, Thailand. It flows through Thung Salaeng Luang National Park and forms Namtok Sri Dit and Namtok Kaeng Sopha in the Wang Thong District of Phitsanulok Province, and finally flows through into the Bang Krathum District, passing through Ban Sam Ruen and on to the border of Phitsanulok and Phichit, where it drains into the Nan River at 16°31′06″N100°19′36″E. The land drained by the Wang Thong River is part of the Nan Basin and the Chao Phraya Watershed.
The Khwae Noi River is a river in northern Thailand. It shares the same name as another river in Thailand, the popular tourist attraction also known as "The River Kwai." These are two distinct bodies of water.
The Wat Ta Yom River is a tributary of the Nan River in Thailand.
Ban Rai is a subdistrict (tambon) in the Bang Krathum District of Phitsanulok Province, Thailand.
Topographical features within the Phitsanulok Province of Thailand include the Phetchabun Mountains, the Nan River and several of its tributaries, waterfalls, swamps, forests, grasslands, caves, a reservoir and an extensive network of canals. Populated areas of the province are largely cleared of natural vegetation and adapted for farming. The land in the province is in the Greater Nan Basin, which is part of the Chao Phraya Watershed. The province includes land within both of the greater Nan basin's sub-basins, i.e., the Nan Basin and Yom Basin. The provincial capital of Phitsanulok is sometimes called Song Kwae, the "city of two rivers", an ancient name dating to a time centuries ago when the Nan and Khwae Noi Rivers met near the city. These two rivers of the Phitsanulok Province are still of major significance to the residents of the region.
The lands situated in the present-day Phitsanulok Province of Thailand have been inhabited since the Stone Age, although the neolithic inhabitants of the region are not likely to have been the ancestors of the modern Thai people who reside there today. The earliest historical records relating to what is now Phitsanulok Province indicates that at a time prior to or during the 11th century, the present-day city of Phitsanulok was but a small strategic Khmer outpost known as Song Khwae. During the next century, in 1188, Nakhon Thai, located near the center of the present Phitsanulok Province, was established as the capital city of the Singhanavati Kingdom, an early city-state of Thailand. Later, during Thailand's Sukhothai Period, the city of Phitsanulok emerged as a major city in the east of the Sukhothai Kingdom, and the great temples of Wat Chula Manee, Wat Aranyik and Wat Chedi Yod Thong were constructed. In 1357, the renowned Wat Phra Sri Rattana Mahathat was erected, and the Ayutthaya Period witnessed the construction of several of the province's other chief temples. Phitsanulok served for 25 years as the capital city of the Ayutthaya Kingdom. In 1555, King Naresuan the Great was born in the city of Phitsanulok. Naresuan played a significant role in the history of Thailand, as he expanded the kingdom to its greatest territorial extent, by conquering sizable portions of modern-day Burma and Cambodia. In recent times, Phitsanulok Province has become an important agricultural center, part of the Bread Basket of Thailand, providing rice and other crops to consumers in Thailand and throughout the world. Extensive agricultural development over the last hundred years or so has spawned a modern infrastructure in the urban areas of the province, bringing with it an array of modern roads, universities, hospitals and other conveniences. Over the years, the Nan River and its tributaries have played a substantial role in the history and development of the region by providing a route for transportation, fertile soil for agriculture, and water for irrigation. The river waters have also served as a route for enemy invaders, and have been the source of periodic widespread flooding throughout the province.
Thailand has 22 river basins with 254 sub-basins. Rainwater is one of the most important sources of water. Thailand's water resource per capita is less than that of other countries in the region.
Nakhon Sawan is a city in Thailand, the name literally means "Heavenly City". The city is the capital of Nakhon Sawan Province, and covers the complete subdistrict (tambon) Pak Nam Pho and parts of Khwae Yai, Nakhon Sawan Tok, Nakhon Sawan Ok and Wat Sai, all of Mueang Nakhon Sawan district. As of 31 December 2020, it has a population of 82,305. Nakhon Sawan is 238 km north of Bangkok.
Phitsanulok is an important, historic city in lower northern Thailand and is the capital of Phitsanulok Province. Phitsanulok is home to Naresuan University and Pibulsongkram Rajabhat University, as well as to a major Royal Thai Army base. As of 2019, the population of the city was 66,106.
The 44th Thailand National Games were held in Nakhon Sawan, Thailand from 12 to 21 December 2015. The opening ceremony, scheduled for 11 December, was postponed by Bike for Dad ปั่นเพื่อพ่อ, to 12 December. There were matches in 43 sports and 77 disciplines. The games were held in Nakhon Sawan Sport Center and Nakhon Sawan sport school. Nakhon Sawan also hosted the 28th national games in 1995.