Gresham (/ˈɡrɛʃəm/ GRESH-əm) is a city in the Willamette Valley, Located in Multnomah County in the U.S. state of Oregon, bordered by Portland to the northwest and partially in the southwest. it was first settled in the early 1850s by the Powell brothers. It remained unincorporated until 1905; it was named after Walter Quintin Gresham, an American Civil War general and United States Secretary of State.

The early economy of the city was primarily supported by agriculture, and by the mid-20th century, the city saw a population boom, increasing from 4,000 residents to more than 10,000 between 1960 and 1970. The population was 114,247 at the 2020 census, making it the second most populous city in the county and the fourth-most populous city in Oregon. Gresham is an economic center for eastern Multnomah County.

The area now known as Gresham was first settled in 1851 by brothers Jackson and James Powell, who laid claim to land under the Donation Land Claim Act of 1850 and named the settlement Powell's Valley. In 1884, a local merchant petitioned for a post office from the United States Post Office Department to be established in his store, proposing to name it after Postmaster General Walter Q. Gresham if his request was granted. Concurrently, other community members secured a post office named "Campground," which referred to the area's religious camp meeting site and its convenience as a stop for travelers heading to Portland. Once the Post Office Department recognized its error, it revoked the Campground post office designation.

Gresham was incorporated in 1905, the year of the Lewis and Clark Centennial Exposition; its population at the time was 365. Lewis Shattuck, a member of a pioneer family, served as the first mayor. The local economy was primarily driven by agriculture, particularly the cultivation of berries, grapes, and vegetables. During that period, trains operated between Gresham and Portland on an hourly schedule. Gresham's early settlers would go on to form the outlying communities of Boring, Sandy, Fairview, and Estacada.

Gresham's city library, which began as a small book collection in the town's general store, was officially established as the Gresham Branch Public Library in 1913 with a grant from the Andrew Carnegie library fund.

Gresham General Hospital opened in 1959 in downtown Gresham. In 1984, the hospital moved to Stark Street and became Mount Hood Medical Center.

According to the United States Census Bureau, the city has a total area of 23.43 square miles (60.68 km2), of which 23.20 square miles (60.09 km2) is land and 0.23 square miles (0.60 km2) is water. The total area includes parts of Fairview Creek and Johnson Creek.

Gresham is characterized by hills on its eastern border. Northeast Gresham is also hilly, especially where the city meets Troutdale toward the Columbia River. Its elevation is 325 feet (99 m). Johnson Creek, which begins at the foothills of the Cascade Mountains, runs westward through Gresham, with 23 percent of the creek's watershed running through the city.

Gresham, like most of western Oregon, has a Mediterranean climate (Köppen Csb/Csa). Summers feature pleasant mornings, very warm and sunny afternoons and only very occasional rainfall, whereas winters are cloudy with cool to cold afternoons, occasional frosts, and frequent long rainy periods.

As of the 2020 census, there were 114,247 people and 44,816 households residing in the city.

As of the 2010 census, there were 105,594 people, 38,704 households, and 25,835 families residing in the city. The population density was 4,551.5 inhabitants per square mile (1,757.3/km2). There were 41,015 housing units at an average density of 1,767.9 per square mile (682.6/km2). The racial makeup of the city was 76.0% White, 3.5% African American, 1.3% Native American, 4.3% Asian, 0.7% Pacific Islander, 9.8% from other races, and 4.5% from two or more races. Hispanic or Latino of any race were 18.9% of the population.

There were 38,704 households, of which 36.9% had children under the age of 18 living with them, 46.6% were married couples living together, 14.3% had a female householder with no husband present, 5.9% had a male householder with no wife present, and 33.2% were non-families. 25.2% of all households were made up of individuals, and 8.8% had someone living alone who was 65 years of age or older. The average household size was 2.69 and the average family size was 3.22.

The median age in the city was 33.6 years. 26.4% of residents were under the age of 18; 10.2% were between the ages of 18 and 24; 28.1% were from 25 to 44; 24.5% were from 45 to 64; and 10.7% were 65 years of age or older. The gender makeup of the city was 49.0% male and 51.0% female.

As of 2000 the median income for a household in the city was $43,442, and the mean income for a family was $51,126. Males had a median income of $37,701 versus $27,744 for females. That is a difference of $9,957. The per capita income for the city was $19,588. About 8.4% of families and 12.5% of the population were below the poverty line, including 17.2% of those under the age of 18 and 6.7% of those 65 and older.

There are several National Register of Historic Places sites located in Gresham. The Louise Home Hospital and Residence Hall, is located in west Gresham, and serves as a social services facility. Other sites include: the Jacob Zimmerman House, a farmhouse built by German-American settlers in 1874; the Hamlin–Johnson House, a farmhouse built in 1888; the Emanuel and Christina Anderson House and William Gedamke House, both Victorian Queen Anne homes built circa 1900; the Gresham Carnegie Library, built in 1913; the Dr. Herbert H. Hughes House, built in 1922; the Charles and Fae Olson House, a modernist home built in 1946; and the David and Marianne Ott House, a ranch home built in 1952.

There are numerous parks in Gresham, such as Main City Park, located near downtown Gresham. Other parks include Hogan Butte Nature Park, East Gresham Park, Pat Pfeifer Park, Thom Park, Red Sunset Park, Rockwood Central Park, Vance Park, and Clatsop Butte Park, an upland butte located south of Powell Butte. Other public points of interest are Persimmon Country Club, Gresham Golf Course Mt. Hood Theatre and Gresham Pioneer Cemetery which was founded in 1859 and lies on the east side of Southwest Walters Road.

The City of Gresham operates under the council–manager form of government. The mayor and city council are elected to be the legislative and policy-making body for the city.

The council appoints a city manager who is responsible for the daily operations of the city. The interim city manager is Eric Schmidt, appointed in December 2023 for a six-month term or until a new city manager is selected.

The city council consists of the mayor and six councilors, all of whom serve four-year terms. Elections are held in November of even-numbered years. In election years divisible by four, (e.g., 2000, 2004, 2008), three councilors are elected. In election years not divisible by four, (e.g., 1998, 2002, 2006), the other three councilors and the mayor are elected.

Gresham is served by three school districts: Centennial, Gresham-Barlow, and Reynolds. High schools include Gresham High School, Sam Barlow High School, Springwater Trail High School, Centennial High School, and Reynolds High School. Private schools include Portland Adventist Elementary School, and Eastside Christian School.

Mount Hood Community College is also located in Gresham, it offers associate degrees, as well as bachelor's programs through a partnership with Eastern Oregon University. According to the US Census, 27.16% of the Gresham residents had a bachelor's degree, while 9.93% had earned a master's degree or above.

Gresham is accessed from the west via Interstate 84 and via U.S. Route 26 from the east.

Gresham is serviced by TriMet's bus system and the MAX Light Rail Blue Line, which includes the following MAX stations:

Gresham is also served by the fareless Sandy Area Metro shuttle bus to Sandy, Oregon.