Mudanjiang (Chinese: 牡丹江; pinyin: Mǔdānjiāng; Manchu: Mudan bira), alternately romanized as Mutankiang, is a prefecture-level city in the southeast part of Heilongjiang province, People's Republic of China. It was called Botankou under Japanese occupation. It serves as a regional transport hub with a railway junction and an international airport connecting with several major Chinese cities as well as Incheon International Airport serving Seoul, South Korea. Mudanjiang is located 248 km (154 mi) from Vladivostok, Russia. In 2011, Mudanjiang had a GDP of RMB 93.48 billion with a 15.1% growth rate. In 2015, Mudanjiang had a GDP of RMB 118.63 billion.

As of the 2020 census Mudanjiang had a population of 2,290,208, of whom 930,051 lived in the 4 urban districts comprising the built-up area of the city. In 2007, the city was listed as one of China's top ten livable cities by Chinese Cities Brand Value Report, which was released at the 2007 Beijing Summit of China Cities Forum.

Mudanjiang was originally populated by the Sushen 2,300 years ago. They lived in the valley of the Mudan River, and established the State of Mo (貊國). During the Tang dynasty, Balhae established their Upper capital Longquan Fu (Yongcheon bu) near Lake Jingpo south of Mudanjiang around 755 AD. On January 14, 926, Yongcheon fell while Balhae was defeated by the Khitans.

Mudanjiang is named after the eponymous Mudan River (literally, "Peony River") flowing through it. Imperial Russia built a train station for the Chinese Eastern Railway in Mudanjiang in 1903, after which local development started boosting. Both Chinese and Russian settlers established themselves here. Mudanjiang was little more than a large village until the 1920s. By that time, Mudanjiang was strongly overshadowed by the nearby county town of Ningan (Former Ninguta). However, merchants from several countries including France, Russia, Britain and Denmark set up sub-agencies in Mudanjiang during this period, which led the trade area of the city to a rapid expansion.^{[citation needed]}

After the Japanese invasion of Manchuria began on September 19, 1931, the whole Manchuria was seized by Japan following the Mukden Incident. Mudanjiang experienced a substantial growth in the 1930s under the Japanese occupation. Mudanjiang also became a military and administrative center going by the name Botankou, particularly after the railway from Tumen to Jiamusi was constructed in 1933. By that time several light industries including light engineering, lumbering, and food processing was established in the town. On December 1, 1937, Botankou City was established by the Manchukuo government, administering five counties. On October 15, 1938, Japanese Government set up a consulate in Botankou and promoted Botankou as a municipality directly under the Manchukuo Government. As Manchukuo collapsed, Mudanjiang was captured by the Soviet Army on August 16, 1945.

Mudanjiang was controlled by the Communist forces and became the capital of Songjiang Province in 1948. However, after Songjiang Province was merged into Heilongjiang Province on June 19, 1954, Mudanjiang was reduced to a prefecture-level city. The historic Beishan Stadium is located in the city. The 15,000-capacity stadium is used mostly for association football matches.^{[citation needed]}

Mudanjiang, spanning from 128° 02' to 131° 18' E longitude and 43° 24' to 45° 59' N latitude, is located in southeastern Heilongjiang province. It is also the province's southernmost prefecture. Neighboring prefectures are:

It also borders Russia's Primorsky Krai to the east. The average elevation in the prefecture is 230 meters (755 ft), with the terrain primarily consisting of mountains and hills. The east of the prefecture begins to ascend to the Changbai Mountains, while the central parts belong to the Hegu Basin. The lowest part of the prefecture is Suifenhe City, bordering Russia, at a minimum elevation of 86.5 meters (283.8 ft), while the highest point is Zhangguangcai mountain, at 1,686.9 meters (5,534 ft).