Seattle is the most populous city in the U.S state of Washington and the Northwestern United States. The encompassing Seattle-Tacoma-Bellevue metropolitan statistical area is the 15th largest in the United States, and the largest in the Pacific Northwest. Seattle is part of the 13th largest combined statistical area (CSA) in the US. A coastal city and major seaport, it is located in the western part of the state between Puget Sound, an arm of the Pacific Ocean, and Lake Washington, about 96 miles (154 km) south of the Canada – United States border. A major economic, cultural and educational center in the region, Seattle is the county seat of King County.

The Seattle area has been inhabited for at least 4,000 years, but European settlement began only in the mid-19th century. The first permanent white settlers—Arthur A. Denny and those subsequently known as the Denny Party—arrived November 13, 1851. Early settlements in the area were called "New York-Alki" ("Alki" meaning "by and by" in the local Chinook Jargon) and "Duwamps." In 1853, Doc Maynard suggested that the main settlement be renamed "Seattle," an anglicized rendition of the name of Sealth, the chief of the two local tribes.

By 2007 Census estimate, the city has a municipal population of 594,210, and a metropolitan area population of 3,263,497.

From 1869 until 1982, Seattle was known as the "Queen City." Seattle's current official nickname is the "Emerald City", the result of a contest held in the early 1980s; the reference is to the lush evergreen trees in the surrounding area. Seattle is also referred to informally as the "Gateway to Alaska," "Rain City," and "Jet City", the latter from the local influence of Boeing. Seattle residents are known as Seattleites.

Seattle is the birthplace of grunge music and has a reputation for heavy coffee consumption; coffee companies founded or based in Seattle include Starbucks, Seattle's Best Coffee, and Tully's. There are also many successful independent artisanal espresso roasters and cafes. Researchers at Central Connecticut State University ranked Seattle the most literate city of America's sixty-nine largest cities in 2005 and 2006, second most literate in 2007 (after Minneapolis), and tied with Minneapolis in 2008. Moreover, analysis conducted by the United States Census Bureau of 2003 survey data indicated that Seattle was the most educated large city in the U.S. with 51.6 percent of residents 25 and older having at least bachelor degrees. Based on per capita income, in 2006 the Seattle metropolitan area ranked 17th out of 363 metropolitan areas in a study by the Census Bureau.

Seattle is located between an inlet of the Pacific Ocean to the west called Puget Sound and Lake Washington to the east. The city's chief harbor, Elliott Bay, is an inlet of the Sound. West beyond the Sound are the Kitsap Peninsula and Olympic Mountains, on the Olympic Peninsula; east beyond Lake Washington and the eastside suburbs are Lake Sammamish and the Cascade Range. Lake Washington's waters flow out through the Lake Washington Ship canal, a series of two man-made canals and Lake Union, to the Hiram C. Chittenden Locks at Salmon Bay, to Shilshole Bay, which is part of Puget Sound. The sea, rivers, forests, lakes, and fields were once rich enough to support one of the world's few sedentary hunter-gatherer societies. Opportunities for sailing, skiing, bicycling, camping, and hiking are nearby and accessible almost year-round.

The city itself is hilly, though not uniformly so. Like Rome, the city is said to lie on seven hills; the lists vary, but typically include Capitol Hill, First Hill, West Seattle, Beacon Hill, Queen Anne, Magnolia, and the former Denny Hill. The Wallingford and Mount Baker neighbourhoods are technically located on hills as well. Many of the hilliest areas are near the city center, with Capitol Hill, First Hill, and Beacon Hill collectively constituting something of a ridge along an isthmus between Elliott Bay and Lake Washington. The break in the ridge between First Hill and Beacon Hill is man-made, the result of two of the many regrading projects that reshaped the topography of the city center. The topography of the city center was also changed by the construction of a seawall and the artificial Harbor Island (completed 1909) at the mouth of the city's industrial Duwamish Waterway.

North of the city center, Lake Washington Ship Canal connects Puget Sound to Lake Washington. It incorporates four natural bodies of water: Lake Union, Salmon Bay, Portage Bay, and Union Bay.

Seattle is in an earthquake zone and has experienced a number of significant quakes, most recently (as of 2007) the magnitude 6.8 Nisqually Earthquake, February 28, 2001, which did significant architectural damage, especially in the Pioneer Square area (built on reclaimed land, as are the Industrial District and part of the city center), but caused no fatalities. Other strong quakes occurred on December 14, 1872 (estimated at 7.3 or 7.4 magnitude), April 13, 1949 (7.1), and April 29, 1965 (6.5). The 1949 quake caused eight known deaths, all in Seattle; the 1965 quake caused three deaths in Seattle directly, and one more by heart failure. Although the Seattle Fault passes just south of the city center, neither it nor the Cascadia subduction zone has caused an earthquake since the city's founding. The Cascadia subduction zone poses the threat of an earthquake of magnitude 9.0 or greater, capable of seriously damaging the city and collapsing many buildings, especially in zones built on fill.

According to the United States Census Bureau, the city has a total area of (142.5 square miles (369 km2)), 83.9 square miles (217 km2) of which is land and 58.7 square miles (152 km2) water. The total area is 41.16 percent water.

Seattle's mild climate is usually classified as Marine west coast (Cfb). However, its wet-winter/dry-summer pattern shows some characteristics of a Mediterranean climate (Csb), and it is sometimes classified this way. Temperature extremes are moderated by adjacent Puget Sound, the greater Pacific Ocean, and Lake Washington. The region is partially protected from Pacific storms by the Olympic Mountains and from Arctic air by the Cascade Range. Despite being on the margin of the rain shadow of the Olympic Mountains, the city has a reputation for frequent rain. This reputation derives from this frequency of precipitation as well as the fact that it is cloudy an average of 226 days per year (cf. 132 in New York City). Nonetheless, the so-called "rainy city" receives a smaller quantity of actual precipitation annually, at 37.1 inches (94 cm), than New York City, Atlanta, Houston, and most cities of the Eastern Seaboard of the United States. Seattle was also not listed in a study that revealed the 10 Rainiest Cities in the continental United States. Most of the precipitation falls as drizzle or light rain, with only occasional downpours. One of these downpours occurred in December 2007 when widespread rainfall hit the greater Puget Sound area. It became the second wettest event in Seattle history when a little over 5 inches of rain fell on Seattle in a 24 hour period. The rain also caused five deaths and widespread flooding and damage. Spring, late fall, and winter are filled with days when it does not rain but looks as if it might because of cloudy, overcast skies. Winters are cool and wet with average lows around 35–40 °F (2–4 °C) on winter nights. Colder weather can occur, but seldom lasts more than a few days. Summers are dry and warm, with average daytime highs around 73–80 °F (22.2–26.7 °C). Hotter weather usually occurs only during a few summer days. Seattle's hottest official recorded temperature was 100 °F (37.8 °C) on July 20, 1994; the coldest recorded temperature was 0 °F (-18 °C) on January 31, 1950.

Eighty miles (130 km) to the west, the Hoh Rain Forest in Olympic National Park on the western flank of the Olympic Mountains receives an annual average rainfall of 142 inches (361 cm), and the state capital, Olympia—south of the rain shadow—receives an annual average rainfall of 52 inches (132 cm). Snowfall is very infrequent, especially at lower altitudes and near the coast, and is usually light and fleeting, lasting only a few days. Heavier snowfall happens infrequently; a recent example happened from December 12-25, 2008, when over one foot of snow fell and stuck on much of the city's roads, causing pandemonium in a city so unaccustomed to heavy snow. Average annual snowfall, as measured at Sea-Tac Airport, is 13 inches (33 cm). Seattle's daily record snowfall was 20 inches (51 cm) on January 13, 1950. A sunnier and drier climate typically dominates from mid-July to mid-September. An average of 0.8 inches (2.0 cm) of rain falls in July and 1.0 inch (2.5 cm) in August. Although the summer climate is considerably drier and less humid than in areas with humid continental climates, a slight dampness can be occasionally felt, usually when temperatures reach above 80 °F (26.7 °C). This dampness is typically more noticeable during the evening when the temperatures have dropped. Because of this, Seattle experiences occasional summer thunderstorms.

The Puget Sound Convergence Zone is an important feature of Seattle's weather. In the convergence zone, air arriving from the north meets air flowing in from the south. Both streams of air originate over the Pacific Ocean; airflow is split by the Olympic Mountains to Seattle's west, then reunited by the Cascade Mountains to the east. When the air currents meet, they are forced upward, resulting in convection. Thunderstorms caused by this activity can occur north and south of town, but Seattle itself rarely receives worse weather than occasional thunder and ice-pellet showers. Nonetheless, the Hanukkah Eve Wind Storm in December 2006 brought heavy rain and winds gusting up to 69 mph (111 km/h). One Seattleite drowned in her collapsed and flooded basement; power failures were widespread, with some left without power for up to eleven days.

An exception to Seattle's dampness often occurs in El Niño years, when the marine weather systems track as far south as California and little precipitation falls in the Puget Sound area. Since the region's water comes from mountain snowpacks during the drier summer months, El Niño winters can not only produce substandard skiing but can result in water rationing and a shortage of hydroelectric power the following summer.

Among Seattle's prominent annual fairs and festivals are the 24-day Seattle International Film Festival, Northwest Folklife over the Memorial Day weekend, numerous Seafair events throughout July and August (ranging from a Bon Odori celebration to hydroplane races), the Bite of Seattle, one of the largest Gay Pride festivals in the United States, and, perhaps most notable of all, the art and music festival Bumbershoot, which programs music as well as other art and entertainment over the Labor Day weekend. All are typically attended by 100,000 people annually, as are Hempfest and two separate Independence Day celebrations. In the past, the Gay Pride parade and festival have been centered on Capitol Hill, but since 2006, festivities have been held city-wide, and the parade has followed a route in Downtown from the retail core to Seattle Center.
The Seattle skyline viewed from Gasworks Park.

Other significant events include numerous Native American powwows, a Greek Festival hosted by St. Demetrios Greek Orthodox Church in Montlake, and numerous ethnic festivals (many associated with Festál at Seattle Center).

There are other annual events, ranging from the Seattle Antiquarian Book Fair & Book Arts Show; an anime convention, Sakura-Con; Penny Arcade Expo, a gaming convention; specialized film festivals, such as the Seattle Gay and Lesbian Film Festival; and a two-day, 9,000-rider Seattle to Portland bicycle ride.

The Henry Art Gallery opened in 1927, the first public art museum in Washington. The Seattle Art Museum (SAM) opened in 1933; SAM opened a museum downtown in 1991 (expanded and reopened 2007); since 1991, the 1933 building has been SAM's Seattle Asian Art Museum (SAAM). SAM also operates the Olympic Sculpture Park (opened 2007) on the waterfront north of the downtown piers. The Frye Art Museum is a free museum on First Hill.

Regional history collections are at the Loghouse Museum in Alki, Klondike Gold Rush National Historical Park, the Museum of History and Industry and the Burke Museum of Natural History and Culture. Industry collections are at the Center for Wooden Boats and the adjacent Northwest Seaport, the Seattle Metropolitan Police Museum, and the Museum of Flight. Regional ethnic collections include the Nordic Heritage Museum, the Wing Luke Asian Museum and the Northwest African American Museum.

Seattle has artist-run galleries, including 10-year veteran Soil Art Gallery, and the newer Crawl Space Gallery.

Woodland Park Zoo opened as a private menagerie in 1889, but was sold to the city in 1899. The Seattle Aquarium has been open on the downtown waterfront since 1977 (undergoing a renovation 2006). The Seattle Underground Tour, an exhibit of places that existed before the Great Fire, is also popular. There are also many community centers for recreation, including Rainier Beach, Van Asselt, Rainier, and Jefferson south of the Ship Canal and Green Lake, Laurelhurst, Loyal Heights north of the Canal, and Meadowbrook.