Portland (/ˈpɔːrtlənd/ PORT-lənd) is the most populous city in the U.S. state of Oregon. Located in the Pacific Northwest at the confluence of the Willamette and Columbia rivers, it is the 28th-most populous city in the United States, sixth most populous on the West Coast, and third most populous in the Pacific Northwest (after Seattle and Vancouver, British Columbia) with a population of 652,503 at the 2020 census. The Portland metropolitan area, with over 2.54 million residents, is the 26th-largest metropolitan area in the nation. Almost half of Oregon's population resides within the Portland metro area. It is the county seat of Multnomah County, Oregon's most populous county.

The Portland area was shaped by massive ice-age floods. It was inhabited by the Chinookan peoples. European American settlers arrived in the 1840s. Portland was named after Portland, Maine, following a coin toss, which is itself named after England's Isle of Portland. In the 19th century, Portland became a major port and lumber center and gained a reputation for saloons and crime. The 20th century saw population growth, World War II shipbuilding, Japanese-American internment, organized crime, and a hippie/counterculture movement. Since the 1990s, it has experienced growth in the technology sector and rising housing costs. It saw major George Floyd protests in 2020–2021.

Portland is located near volcanic features such as Mount Tabor and within reach of active faults. The city is divided into six addressing sectors and comprises diverse neighborhoods. Portland has a predominantly White population. The city’s economy is driven by technology, athletic and outdoor brands, shipping, and craft industries. Social issues include homelessness and crime, although recent trends indicate a decline in violent crime. As of 2025, the city has the second-highest property crime rate in United States, though it has a low violent crime rate. The city prioritizes urban planning, sustainability, and diverse transportation options, while managing growth with an urban growth boundary. Portland also has numerous schools and universities, media outlets, healthcare facilities, and global sister-city connections.

The city operates with a mayor–council government system, guided by a mayor and 12 city councilors, as well as Metro, the only directly elected metropolitan planning organization in the United States. Its climate is marked by warm, dry summers and cool, rainy winters. This climate is ideal for growing roses, and Portland has been called the "City of Roses" for over a century. Portland is known for its vibrant music and performing arts scene, extensive parks including Forest Park, and professional sports teams such as the Trail Blazers, Timbers, and Thorns.

During the prehistoric period, the land that would become Portland was flooded after the collapse of glacial dams from Lake Missoula, in what would later become Montana. These massive floods occurred during the last ice age and filled the Willamette Valley with 300 to 400 feet (91 to 122 m) of water.

Before American settlers began arriving in the 1800s, the land was inhabited for many centuries by two bands of indigenous Chinook people – the Multnomah and the Clackamas. The Chinook people occupying the land were first documented in 1805 by Meriwether Lewis and William Clark. Before its European settlement, the Portland Basin of the lower Columbia River and Willamette River valleys had been one of the most densely populated regions on the Pacific Coast.

Large numbers of pioneer settlers began arriving in the Willamette Valley in the 1840s via the Oregon Trail with many arriving in nearby Oregon City. A new settlement then emerged ten miles from the mouth of the Willamette River, roughly halfway between Oregon City and Hudson's Bay Company's Fort Vancouver. This community was initially referred to as "Stumptown" and "The Clearing" because of the many trees cut down to allow for its growth. In 1843 William Overton saw potential in the new settlement but lacked the funds to file an official land claim. For 25 cents, Overton agreed to share half of the 640-acre (2.6 km²) site with Asa Lovejoy of Boston.

In 1844, Overton sold his remaining half of the claim to Francis W. Pettygrove of Portland, Maine. Both Pettygrove and Lovejoy wished to rename "The Clearing" after their respective hometowns (Lovejoy's being Boston, and Pettygrove's, Portland). This controversy was settled with a coin toss that Pettygrove won in a series of two out of three tosses, thereby providing Portland with its namesake. The coin used for this decision, now known as the Portland Penny, is on display in the headquarters of the Oregon Historical Society. At the time of its incorporation on February 8, 1851, Portland had over 800 inhabitants, a steam sawmill, a log cabin hotel, and a newspaper, the Weekly Oregonian. A major fire swept through downtown in August 1873, destroying twenty blocks on the west side of the Willamette along Yamhill and Morrison Streets, and causing $1.3 million in damage, roughly equivalent to $34.1 million today. By 1879, the population had grown to 17,500 and by 1890 it had grown to 46,385. In 1888, the first steel bridge on the West Coast was opened in Portland, the predecessor of the 1912 namesake Steel Bridge that survives today. In 1889, Henry Pittock's wife, Georgiana, established the Portland Rose Society. The annual Portland Rose Festival" is held here in June. The movement to make Portland a "Rose City" started as the city was preparing for the 1905 Lewis and Clark Centennial Exposition.