Omaha ( OH-mə-hah) is the largest city in the U.S. state of Nebraska and the county seat of Douglas County. Omaha is in the Midwestern United States on the Missouri River, about 10 mi (15 km) north of the mouth of the Platte River. The nation's 39th-largest city, Omaha's 2020 census population was 486,051.

Omaha is the anchor of the eight-county, bi-state Omaha-Council Bluffs metropolitan area. The Omaha Metropolitan Area is the 58th-largest in the United States, with a population of 967,604. The Omaha-Council Bluffs-Fremont, NE-IA Combined Statistical Area (CSA) totaled 1,004,771, according to 2020 estimates. Approximately 1.5 million people reside within the Greater Omaha area, within a 50 mi (80 km) radius of Downtown Omaha. It is ranked as a global city by the Globalization and World Cities Research Network, which in 2020 gave it "sufficiency" status.

Omaha's pioneer period began in 1854, when the city was founded by speculators from neighboring Council Bluffs, Iowa. The city was founded along the Missouri River, and a crossing called Lone Tree Ferry earned the city its nickname, the "Gateway to the West". Omaha introduced this new West to the world in 1898, when it played host to the World's Fair, dubbed the Trans-Mississippi Exposition. During the 19th century, Omaha's central location in the United States spurred the city to become an important national transportation hub. Throughout the rest of the 19th century, the transportation and jobbing sectors were important in the city, along with its railroads and breweries. In the 20th century, the Omaha Stockyards, once the world's largest, and its meatpacking plants gained international prominence.

Today, Omaha is the home to the headquarters of four Fortune 500 companies: conglomerate Berkshire Hathaway; one of the world's largest construction companies, Kiewit Corporation; insurance and financial firm Mutual of Omaha; and the United States' largest railroad operator, Union Pacific Corporation. Berkshire Hathaway is headed by local investor Warren Buffett, one of the wealthiest people in the world, according to a decade's worth of Forbes rankings, some of which have ranked him as high as No. 1.

Omaha is also the home to five Fortune 1000 headquarters: Green Plains, Intrado, TD Ameritrade, Valmont Industries, and Werner Enterprises. Also headquartered in Omaha are the following: First National Bank of Omaha, the third largest privately held bank in the United States; three of the nation's ten largest architecture/engineering firms (DLR Group, HDR, Inc., and Leo A Daly); and the Gallup Organization, of Gallup Poll fame, and its riverfront Gallup University.

Notable modern Omaha inventions include the following: the "pink hair curler" created at Omaha's Tip-Top Products; Butter Brickle Ice Cream, and the Reuben sandwich, conceived by a chef at the then–Blackstone Hotel on 36th and Farnam Streets; cake mix, developed by Duncan Hines, then a division of Omaha's Nebraska Consolidated Mills, the forerunner to today's ConAgra Foods; center-pivot irrigation by the Omaha company now known as Valmont Corporation; Raisin Bran, developed by Omaha's Skinner Macaroni Co.; the first ski lift in the U.S., in 1936, by Omaha's Union Pacific Corp.; the Top 40 radio format, pioneered by Todd Storz, scion of Omaha's Storz Brewing Co. and head of Storz Broadcasting, and first used in the U.S. at Omaha's KOWH Radio; and the TV dinner, developed by Omaha's Carl A. Swanson.