The Peter the Great Gulf (Russian: Залив Петра Великого) is a gulf on the southern coast of Primorsky Krai, Russia, and the largest gulf of the Sea of Japan. The gulf extends for 185 km (115 mi) from the Russian-Chinese border at the mouth of the Tumen River in the west across to Cape Povorotny in the east, and its bays reach 90 km (56 mi) inland. Vladivostok, the largest city and capital of Primorsky Krai, and Nakhodka, the third largest city in the Krai, are located along the coast of the gulf.
The Peter the Great Gulf has a coastline of about 1,500 km (930 mi), with the largest bay of the gulf of about 6,000 km2 (2,300 sq mi) divided by the Muravyov-Amursky Peninsula and the Eugénie Archipelago into the major bays of Amur Bay to the west and the Ussuri Bay to the east. The coast is indented by many smaller minor bays, including Possiet Bay, the Zolotoy Rog (the "Golden Horn"), and Diomede Bay in the west, Lazurnaya Bay (the "Shamora", with its sand beaches) in the Muravyov-Amursky Peninsula, and Strelok, Vostok and Nakhodka Bay to the east. The functioning of these bays as harbours is severely limited by the freezing from early December to mid-April.
The Peter the Great Gulf contains numerous islands, including the Rimsky-Korsakov Archipelago and Furugelm Island to the west, and Askold Island and Putyatin Island to the east. The Eugénie Archipelago is separated from the Muravyov-Amursky Peninsula by the Eastern Bosphorus, which runs between Vladivostok and Russky Island, the largest island in the archipelago and Primorsky Krai. In 2012, Russky Island was connected to the mainland by the Russky Bridge.
About 630 km2 (240 sq mi) of the gulf area is protected as the Far Eastern Marine Nature Reserve. Even though large whales have become very rare in the area today, eight species of cetaceans are known to migrate into the gulf. Common minke whales often swim nearby shores of the coastal towns, and Beluga whales are known to migrate to Rudnaya Bay in the north and occasional appearances around Vladivostok.  The gulf's coastline is also frequented by seals and Steller's sea lions.
Historically the Peter the Great Gulf belonged to the region known as Manchuria, ruled by the Jurchen people that became part of the Manchu, who later became the rulers of China in the Qing Dynasty. In the nineteenth century, the region unofficially known as Outer Manchuria was gradually ceded by the Qing to the Russian Empire, with the Convention of Peking in 1860 transferring the lands containing the gulf, which later became Primorsky Krai. Initially from 1855 the gulf known as Victoria Bay, but in 1859 it was renamed to Peter the Great Gulf in honour of Tsar Peter the Great. The Manza War in 1868 was the first attempt by Russia to forcibly expel ethnic Chinese from territory it controlled. Hostilities broke out around Peter the Great Gulf when the Russians tried to shut off gold mining operations and expel Chinese workers near Vladivostok. The Chinese resisted a Russian attempt to take Askold Island and in response, two Russian Army military stations and three Russian towns were attacked by the Chinese, and the Russians failed to oust the Chinese.
Between 5–12 July 2013, warships from the Russian Navy's Russian Pacific Fleet and the People's Liberation Army Navy's North Sea Fleet participated in Joint Sea 2013, which were bilateral naval maneuvers held in the Peter the Great Gulf. Joint Sea 2013 was the largest naval drill yet undertaken by the People's Liberation Army Navy with a foreign navy.
Probably the first clash between the Russians and Chinese occurred in 1868. It was called the Manza War, Manzovskaia voina. "Manzy" was the Russian name for the Chinese population in those years. In 1868, the local Russian government decided to close down goldfields near Vladivostok, in the Gulf of Peter the Great, where 1,000 Chinese were employed. The Chinese decided that they did not want to go back, and resisted. The first clash occurred when the Chinese were removed from Askold Island,
in the Gulf of Peter the Great. They organized themselves and raided three Russian villages and two military posts. For the first time, this attempt to drive the Chinese out was unsuccessful.