Si Nan National Park (Thai: อุทยานแห่งชาติศรีน่าน) is a national park in Thailand's Nan Province. This mountainous park is home to steep cliffs and a long section of the Nan River. It was established on May 25, 2007.

Si Nan National Park is about 80 kilometres (50 mi) south of the town of Nan in the Wiang Sa, Na Noi, and Na Muen districts of Nan Province. The park's area is 640,237 rai ~ 1,024 square kilometres (395 sq mi). The park's highest point is the Khao Khun Huai Huek peak at 1,234 metres (4,049 ft). The Nan River flows for about 60 kilometres (40 mi) through the park.

Pha Chu, Pha Hua Sing, and Doi Samer Dao offer scenic views of the park's mountainous terrain. Kaeng Luang is a popular rafting spot along the Nan River.

The park features forest types including deciduous and mixed. Tree species include Irvingia malayana, krabak, Malabar ironwood, makha, Xylia xylocarpa, Dalbergia oliveri and Vitex pinnata.

Park animals, some of which are endangered species, include tiger, leopard, fishing cat, wild boar, mouse deer, masked palm civet, Asiatic wild dog (dhole) and treeshrew.

Si Nan National Park in overview PARO 13 (Phrae)
National park 1 Doi Pha Klong 2 Doi Phu Kha 3 Khun Nan 4 Khun Sathan 5 Mae Charim 6 Mae Yom 7 Nanthaburi 8 Si Nan 9 Tham Sakoen 10 Wiang Kosai   Wildlife sanctuary 11 Doi Luang 12 Lam Nam Nan Fang Khwa      Non-hunting area 13 Chang Pha Dan 14 Phu Fa   Forest park 15 Doi Mon Kaeo–Mon Deng 16 Pha Lak Muen 17 Phae Mueang Phi 18 Tham Pha Tub

• List of national parks of Thailand
• List of Protected Areas Regional Offices of Thailand