Cairns (/ˈkɛərnz/ ^ⓘ; Yidiny: Gimuy) is a city in the Cairns Region, Queensland, Australia, on the tropical north east coast of Far North Queensland. In the 2021 census, Cairns had a population of 169,312 people.

The city was founded in 1876 and named after Sir William Wellington Cairns, following the discovery of gold in the Hodgkinson River. During World War II, the city became a staging ground for the Allied Forces in the Battle of the Coral Sea. By the late 20th century the city had become a centre of international tourism. In the early 21st century, it has developed into a major regional city.

The economy of Cairns is based primarily on tourism, healthcare and education, along with a major capacity in aviation, marine and defence industries. The city has a gross regional product at about $12.2 billion as of 2024. The city is served by Cairns International Airport, the seventh-busiest airport in Australia. Cairns also has a major cruise ship industry servicing both domestic and international markets, with terminals at Cairns Seaport and Cairns Wharf Complex.

Cairns is a major tourist destination, with access to two UNESCO world heritage sites: the Daintree Rainforest as part of the Wet Tropics of Queensland, and the Great Barrier Reef, one of the seven natural wonders of the world.

Prior to British settlement, the Cairns area was inhabited by the Gimuy Walubara Yidinji people, who still claim their native title rights. Yidinji (also known as Yidinj, Yidiny, and Idindji) is an Australian Aboriginal language. Its traditional language region is within the local government areas of Cairns Region and Tablelands Region, in such localities as Cairns, Gordonvale, and the Mulgrave River, and the southern part of the Atherton Tableland including Atherton and Kairi. The area in which the city is located is known in the local Yidiny language as Gimuy, and the clan who inhabited the region before colonisation are the Gimuy-walubarra clan.

From 1770 to the early 1870s, the area was known to the British simply as Trinity Bay. The arrival of beche de mer fishermen from the late 1860s saw the first European presence in the area. On the site of the modern-day Cairns foreshore, there was a large native well which was used by these fishermen. A violent confrontation occurred in 1872 between local Yidinji people and Phillip Garland, a beche de mer fisherman, over the use of this well. The area from this date was subsequently called Battle Camp.

In 1876, hastened by the need to export gold mined from the Hodgkinson goldfields on the tablelands to the west, closer investigation by several official expeditions established its potential for development into a port. Brinsley G. Sheridan surveyed the area and selected a place further up Trinity Inlet known to the diggers as Smith's Landing for a settlement which he renamed Thornton. However, after Native Police officers Alexander Douglas-Douglas and Robert Arthur Johnstone opened a new track from the goldfields to Battle Camp, this more coastal site became preferable. The area was named Cairns in late 1876 in honour of the then Governor of Queensland, William Cairns. The site was predominantly mangrove swamps and sand ridges. Labourers gradually cleared the swamps, and the sand ridges were filled with dried mud, sawdust from local sawmills, and ballast from a quarry at Edge Hill.

Throughout the late 19th century, Cairns prospered from the settlement of Chinese immigrants who helped develop the region's agriculture. Soon after Cairns was established "a few entrepreneurial Chinese men began to experiment with crops such as cotton, tobacco, coffee, rice, sugar, and bananas, while market gardeners grew much needed fruit and vegetables. This marked the beginning of the agricultural industry, which became the dominant industry." "The growing agricultural industry in the Cairns region provided the impetus for Cairns Chinatown to develop as Chinese men turned to support industries such as market gardening and shop keeping. They were not only ex-miners, but a growing number of immigrants arriving directly from China to take advantage of the agricultural boom. In 1886 the Chinese population accounted for 60% of all farmers and 90% of gardeners, that is 795 cultivators and gardeners."