Western Australia, state in western Australia that occupies the region of the continent that is the most remote from the continent's major cultural centers to the east. To the north, the state is bounded by the Timor Sea; to the northwest and west, by the Indian Ocean; and to the south, by the portion of the Indian Ocean known in Australia as the Southern Ocean (or Antarctic Ocean). To the east are the Northern Territory and South Australia's deserts. Perth is the capital.

Western Australia accounts for roughly one-third of the continent's total land area. It stretches approximately 1,490 miles (2,400 kilometers) from the monsoonal, tropical north to the far south's windswept coastal heaths. The majority of the state is subarid, and the combination of low rainfall and high temperatures confines the majority of the population and agricultural activities to an imaginary line stretching from north of Geraldton on the state's western coast to Esperance on the state's southern coast. The vast majority of the population resides in the greater Perth area, which is one of Australia's largest metropolitan areas. Perth is one of the world's most isolated administrative capitals, being closer to Jakarta and Singapore in terms of distance and time zone than it is to Sydney.

Western Australia's landscape is dominated by broad plateaus articulated by several mountain ranges in the north and west; to the east are vast deserts. In the far north, the Kimberley region is a multi-sectioned plateau. The coast is rugged and dangerous, with strong currents and a tidal range of up to 39 feet (12 metres), while the rolling inland areas are sparsely forested and dotted with bristly grasses. The limestone King Leopold Ranges rise from the region's south. The Fitzroy and Ord rivers form the Kimberley's southern and eastern borders.

To the south of the Kimberley region are the Great Sandy Desert's linear sand dunes, which range in height from 26 to 30 feet (8 to 9 meters). Although the primary dune formation phase ended approximately 10,000 years ago, the dune crests remain active (shifting). The Great Sandy Desert extends southward into the state's central interior, where it merges imperceptibly with the Gibson Desert, which in turn gives way to the Great Victoria Desert.

The Pilbara region lies southwest of the Great Sandy Desert, a rugged, arid landscape of ancient folded and uplifted rocks. At the so-called North Pole, some of the world's oldest fossil stromatolites (made of algae and limestone) can be found. They date back approximately 3.5 billion years. In Karijini National Park, the region is home to the spectacular red gorges of the Hamersley Range. Mount Meharry, Western Australia's highest peak at 4,111 feet (1,253 meters), is nearby, approximately 175 miles (280 kilometers) from the central coast. On the coast proper, the arid Cape Range is formed by limestone ranges and gorges on the peninsula to the west of Exmouth Gulf.

Further south, and encompassing the majority of Western Australia's southwestern segment, is the Yilgarn block, a stable granite-gneiss shield area, or craton, that is similar in many ways to the Canadian Shield. Unlike the Canadian Shield, the Western Australian craton, on the other hand, has been weathered for approximately 250 million years. Between 1,000 and 2,000 feet (300 and 600 metres) above sea level, the gently undulating, weathered plateau of the Yilgarn block is located. It is bounded on the east by the Nullarbor Plain, a flat, waterless, treeless marine limestone plateau that terminates in an unbroken line of spectacular coastal cliffs at the Southern Ocean. To the west, the Darling Range scarp runs north-south for approximately 200 miles (320 kilometers), separating the Yilgarn block from the Perth Basin's coastal plain. In the extreme south, the block rises to 3,596 feet (1,096 metres) in the Stirling Range and then plunges abruptly into the ocean, creating a rugged granite coastline with clean, white sand bays. Offshore, granite island archipelagos exist.

Northern and southern Western Australia have climates that are diametrically opposed; the north has a tropical climate with summer rainfall, while the south has a Mediterranean climate. For about half of the year, the weather is largely determined by the movement of an anticyclone, which generates east-west winds across the continent. In the winter, this system moves northward and is responsible for the tropics' clear skies, sunny days, and easterly winds. To the south of the anticyclonic system, westerly winds and a succession of cold fronts associated with the "roaring forties" (windy zone between 40° and 50° S) bring cool, cloudy weather, rain, and westerly gales along the southern coast. By the summer, the anticyclonic belt had moved so far south that its axis was off the southern coast. Over the majority of the state, easterly winds prevail, but a depression forms in the far north, bringing westerly monsoon (wet-dry) wind patterns to the coastal districts northeast of Onslow and parts of the Kimberley.

Numerous tropical cyclones (otherwise known as hurricanes or typhoons) form offshore during the northern wet season, which runs roughly from December to March. Between Broome and Onslow, they frequently migrate inland, although they have occasionally traveled south of Perth before curving inland. Tropical cyclones can be extremely destructive, but they can also be extremely beneficial, bringing widespread rain to parched inland areas.

The extreme north, on the Mitchell Plateau in the Kimberley, and the extreme southwest, between Pemberton and Walpole in karri (Eucalyptus diversicolor) country, receive the most annual precipitation. In both locations, the average annual rainfall exceeds 55 inches (1,400 mm). Precipitation decreases as one travels south and north from both locations, and as one travels inland from the coast. Annual precipitation in the driest areas is less than 8 inches (200 mm), and possibly less than 6 inches (150 mm).

November is the hottest month in the Kimberley, December is the hottest month further south, and January/February is the hottest month in the rest of the state. July is the coldest month of the year. Wyndham is the most consistently hot location, with an average maximum monthly temperature of approximately 96 degrees Fahrenheit (35.6 degrees Celsius) throughout the year. Marble Bar has the highest seasonal mean maximum monthly temperatures in Australia, with temperatures hovering near 100 degrees Fahrenheit (38 degrees Celsius) from November to March. In the southwest, sea breezes (dubbed the "Fremantle Doctor" by Perth residents) blow most afternoons during the hot months, providing relief from the high temperatures along the populated coast.

During the winter, temperatures may fall below freezing across the majority of the state's inland region south of the Tropic of Capricorn; on occasion, temperatures have dropped to the low 20s F (about 6 °C) in the state's southwestern region. Frosts are common in the southern part of the state and occasionally extend into the tropical zone, but they are rarely bothersome. They are most prevalent during the months of July and August. Snow is uncommon, and only in the south, particularly in the Stirling Range, does it occasionally fall for a few hours.

Western Australia's economy is largely dependent on unprocessed primary products—primarily mining, but also agriculture (including pastoralism), horticulture, and, to a lesser extent, forestry and fishing. In the latter half of the twentieth century, the value of agricultural production and exports increased overall but decreased proportionately, while the value of mineral (including petroleum and natural gas) extraction and export increased. Despite its size and resource wealth, Western Australia's economy contributes a relatively small portion of Australia's overall gross domestic product (GDP).