Port Moresby (; Tok Pisin: Pot Mosbi), also referred to as Pom City or simply Moresby, is the capital and largest city of Papua New Guinea. It is one of the largest cities in the southwestern Pacific (along with Jayapura) outside of Australia and New Zealand. It is located on the shores of the Gulf of Papua, on the south-western coast of the Papuan Peninsula of the island of New Guinea. The city emerged as a trade centre in the second half of the 19th century. During World War II, it was a prime objective for conquest by the Imperial Japanese forces during 1942–43 as a staging point and air base to cut off Australia from Southeast Asia and the Americas. Due to its population and outsized influence compared to other cities in Papua New Guinea, Port Moresby may be regarded as a primate city.

As of the 2011 census, Port Moresby had 364,145 inhabitants. An unofficial 2020 estimate gives the population as 383,000. The place where the city was founded has been inhabited by the Motu-Koitabu people for centuries. The first Briton to see it was Royal Navy Captain John Moresby in 1873. It was named in honour of his father, Admiral of the Fleet Sir Fairfax Moresby.

Although Port Moresby is surrounded by Central Province, of which it is also the capital, it is not part of that province but forms the National Capital District. The traditional landowners, the Motu and Koitabu people, are represented by the Motu Koita Assembly.

Port Moresby hosted the APEC summit in November 2018. However, there were concerns about security given the capital's reputation for violent crime.