Luhansk (UK: /luːˈhænsk/, US: /-ˈhɑːn-/; Ukrainian: Луганськ, IPA: [lʊˈɦɑnʲsʲk] ^ⓘ), also known as Lugansk (UK: /-ˈɡæn-/, US: /-ˈɡɑːn-/; Russian: Луганск, IPA: [lʊˈɡansk] ^ⓘ), is a city in the Donbas in eastern Ukraine. As of 2022, the population was estimated to be 397,677 (2022 estimate), making Luhansk the 12th-largest city in Ukraine.

Luhansk served as the administrative center of Luhansk Oblast, before pro-Russian separatists seized control of the city in 2014 and made it the capital of the self-proclaimed Luhansk People's Republic. The Ukrainian administration was located in Sievierodonetsk from 2014 to 2022 during the war in Donbas, due to Ukraine not being in control of Luhansk. Sievierodonetsk was captured by Russia in 2022 and Luhansk Oblast was later annexed by Russia in late 2022.

The city was founded as a foundry in 1795-1796, following the decree of Empress Catherine II titled On the establishment of a foundry in the Donetsk uyezd by the Lugan River. The settlement that developed around the plant was named Lugansk, deriving its name from the hydronym Lugan, which itself originates from the Russian word lug (meadow). The settlement was granted city status in 1882.

In 1935, the city was renamed Voroshilovgrad in honor of the Soviet political and military figure Kliment Voroshilov. Following the adoption of a 1957 decree by the Presidium of the Supreme Soviet of the USSR, which prohibited naming populated places after living political figures, the city's original name, Lugansk, was restored in 1958. However, in 1970, after Voroshilov's death, the city was once again renamed Voroshilovgrad. In 1990, the name Luhansk was reinstated.

The city traces its history to 1797 when the British industrialist Charles Gascoigne, commissioned by the Imperial Russian government in 1795, founded an ammunition and cannon factory for the Black Sea Fleet. Gascoigne had emigrated to Saint Petersburg years earlier, and founded factories and mines across the Russian Empire during his time there. There is a prominent bust of him in Luhansk commemorating his role in the city's founding.

The factory was built in the Donets Basin (or Donbas) at the confluence of the Luhan and Vilkhivka [uk] rivers. The Russian craftsmen settled upstream, at the settlement of Kamianyi Brid. The name "Luhansk" comes from the Luhan River, which flows through the city. According to folk etymology, the name is also derived to the word "Luh" (Ukrainian: Луг), which means "meadow", referring to the floodplains around the river.^{[citation needed]}

The factory was greatly expanded during the Napoleonic Wars, and again during the Crimean War. By 1880, the factory was a large industrial node, linked by rail to other major cities and to the Azov Sea. In 1882, the Luhansk Factory was merged with Kamianyi Brid into a new settlement named Luhansk, which received city status. In 1897, Luhansk had a population of 20,400, 68.2% of whom were Russians.

In summer 1896, German industrialist Gustav Hartmann [de] founded a locomotive-building company in Luhansk, which is now Luhanskteplovoz. It became operational in 1900, and soon produced a large proportion of all locomotives in the Russian Empire.