Asia ( AY-zhə, UK also AY-shə) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which has long been home to the majority of the human population, was the site of many of the first civilisations. Its estimated 4.8 billion people in 2025 constituted approximately 59% of the world's population.

Asia shares the landmass of Eurasia with Europe, and of Afro-Eurasia with both Europe and Africa. In general terms, it is bounded on the east by the Pacific Ocean, on the south by the Indian Ocean, and on the north by the Arctic Ocean. The border of Asia with Europe is a historical and cultural construct, as there is no clear physical or geographical separation between them. A commonly accepted division places Asia east of the Suez Canal, which separates it from Africa; and east of the Turkish Straits, the Ural Mountains, and the Ural River, and south of the Caucasus Mountains and the Caspian and Black Seas, which separate it from Europe.

Since the concept of Asia derives from the term for the eastern region from a European perspective, Asia is the remaining vast area of Eurasia minus Europe. Therefore, Asia is a region where various independent cultures coexist rather than sharing a single culture, and its boundary with Europe is somewhat arbitrary and has moved since its first conception in classical antiquity. The division of Eurasia into two continents reflects East–West cultural differences, some of which vary on a spectrum.

China and India traded places as the largest economies in the world from 1 to 1800 CE. The Silk Road became the main east–west trading route in the Asian hinterlands, while the Straits of Malacca stood as a major sea route. Asia has exhibited economic dynamism as well as robust population growth during the 20th century, but overall population growth has since fallen. Asia was the birthplace of most of the world's mainstream religions, including Islam, Judaism, Christianity, Hinduism, Buddhism, and many other religions.

Asia varies greatly across and within its regions with regard to ethnic groups, cultures, environments, economics, historical ties, and government systems. It also has a mix of many different climates ranging from the equatorial south via the hot deserts in parts of West Asia, Central Asia, South Asia, and East Asia and tropical jungles in Southeast Asia, temperate areas in the east and the continental centre to vast subarctic and polar areas in North Asia.