Neptune's design is based on the Soviet Kh-35 subsonic anti-ship missile, with substantially improved range, targeting and electronics equipment.

The system requirement was for a single missile to defeat surface warships and transport vessels with a displacement of up to 9,000 tonnes, either in convoys or moving individually.

[citation needed] The first tests of the system were conducted on 22 March 2016, attended by Secretary of the National Security and Defense Council (NSDC) Oleksandr Turchynov.

[8] On 17 August 2018, the missile successfully hit a target at a range of 100 kilometres (62 mi) during test firings in southern Odesa Oblast.

Ukraine signed a memorandum with Indonesia on concluding a contract for the supply of Neptune missiles, first reported in December 2020.

[11] Thus, Indonesia may become the first foreign buyer of Neptune, according to Defense Express [uk] with reference to the Ukrainian special exporter State Enterprise (SE) "Progress".

[13] Later, Oleksiy Arestovych, a freelance adviser to the Office of the President of Ukraine, clarified that Admiral Essen had been hit by a Neptune missile.

[14][15] On 13 April 2022, Ukrainian sources claimed the Russian cruiser Moskva was hit by two Neptune missiles, resulting in a fire and subsequent explosion of a shipboard ammunition store.

[20][21] According to Thomas Shugart, a former U.S. Navy submarine commander, Slava-class cruisers like Moskva have been typically "known for their offensive punch, not for their defensive systems or their damage control".

[28] One day earlier, two Russian vessels in Sevastopol were heavily damaged by either Neptune or Storm Shadow cruise missiles.

[31] On 21 April 2024, a video was released from Sukharnaya Bay, Sevastopol, that allegedly shows the salvage ship Kommuna hit by a Ukrainian Neptune missile.

[35] On 31 July 2024, a Neptune struck an airbase in Kursk, Russia, one hundred kilometres from the border with Ukraine, hitting "a warehouse for storing weapons and military equipment," according to Ukrainian officials.

[37] On the morning of 21 August 2024, the Ukrainian military claimed to have struck a Russian S-300 air defense system in Rostov Oblast overnight, possibly by using a Neptune missile.