Tustin is a city located in Orange County, California, United States, within the Los Angeles metropolitan area. In 2020, Tustin had a population of 80,276. The city does not include the unincorporated community of North Tustin.

On November 1, 1776, Mission San Juan Capistrano became the area's first permanent European settlement in Alta California, New Spain.

In 1801, the Spanish Empire granted 62,500 acres (253 km2) to José Antonio Yorba, which he named Rancho San Antonio. Yorba's great rancho included the lands where the cities and communities of Olive, Orange, Villa Park, Santa Ana, Tustin, Costa Mesa and Newport Beach stand today. Smaller ranchos evolved from this large rancho including the Rancho Santiago de Santa Ana.

After the Mexican–American War, Alta California became part of the United States and American settlers arrived in this area. Columbus Tustin, a carriage maker from Northern California, founded the city in 1868 on 1,300 acres (5.3 km2) of land from the former Rancho Santiago de Santa Ana. The city was incorporated in 1927 with a population of about 900. The townsite was bordered by Camino Real on the south, Newport Avenue on the east, 1st Street on the north, and Route 43, now known as the Costa Mesa Freeway, on the west.

During World War II, a Navy anti-submarine airship base (later to become a Marine Corps helicopter station) was established on unincorporated land south of the city; the two dirigible hangars are among the largest wooden structures ever built and are listed on the National Register of Historic Places and ASCE List of Historic Civil Engineering Landmarks. The north hangar burned down in 2023.

Suburban growth after the war resulted in increased population, annexation of nearby unincorporated land including the former Marine Corps Air Station, and development of orchards and farmland into housing tracts and shopping centers.

According to the U.S. Census Bureau, the city has a total area of 11.1 square miles (28.7 km2). It is bordered by Irvine on the south and east, Orange and the unincorporated community North Tustin on the north, and Santa Ana on the west.

The city is sometimes referred to as "The City of Trees". Sycamores and oaks, native to the area, grew in abundance at the time of the founding of the city, and city founder Columbus Tustin was responsible for planting many more along the streets of the city.

Tustin has a Mediterranean climate (Köppen climate classification Csa).

The 2020 United States census reported that Tustin had a population of 79,430. The population density was 6,816.7 per square mile (2,631.9/km2). The racial makeup was 39,729 (52.6%) White (34.8% Non-Hispanic White), 1,722 (2.3%) African American, 442 (0.6%) Native American, 15,299 (20.3%) Asian, 268 (0.4%) Pacific Islander, 14,499 (19.2%) from other races, and 3,581 (4.7%) from two or more races. There were 30,024 people of Hispanic or Latino origin, of any race (39.7%).

The census reported that 75,020 people (99.3% of the population) lived in households, 340 (0.5%) lived in non-institutionalized group quarters and 180 (0.2%) were institutionalized.

There were 25,203 households, of which 10,465 (41.5%) had children under the age of 18 living in them, 12,969 (51.5%) were opposite-sex married couples living together, 3,494 (13.9%) had a female householder with no husband present, 1,472 (5.8%) had a male householder with no wife present. There were 1,568 (6.2%) unmarried opposite-sex partnerships and 193 (0.8%) same-sex married couples or partnerships. 5,178 households (20.5%) were one person and 1,403 (5.6%) had someone living alone who was 65 or older. The average household size was 2.98. There were 17,935 families (71.2% of households) and the average family size was 3.46.

The age distribution was 20,212 people (26.8%) under the age of 18, 6,856 (9.1%) aged 18 to 24, 25,033 (33.1%) aged 25 to 44, 17,006 (22.5%) aged 45 to 64, and 6,433 (8.5%) who were 65 or older. The median age was 33.4 years. For every 100 females, there were 94.7 males. For every 100 females age 18 and over, there were 91.6 males.

There were 26,476 housing units at an average density of 2,389.2 per square mile (922.5/km2). Of the occupied units, 12,813 (50.8%) were owner-occupied and 12,390 (49.2%) were rented. The homeowner vacancy rate was 1.3%; the rental vacancy rate was 5.8%. 36,783 people (48.7% of the population) lived in owner-occupied housing units and 38,237 people (50.6%) lived in rental housing units.

According to the 2010 census, Tustin had a median household income of $74,011, with 12.2% of the population living below the federal poverty line.

According to the city's 2020 Comprehensive Annual Financial Report, the top employers in the city are:

The Tustin City Council is composed of five members elected at large; the mayorship rotates among the council members and is primarily a ceremonial role.

Mayor Allan Bernstein was elected to the Tustin City Council in 2012. In 2019, Letitia Clark was chosen to serve as mayor pro tem, Charles E. "Chuck" Puckett, Barry Cooper and Austin Lumbard are also on the City Council as council members.

Local politics in the late 1990s and early 2000s were dominated by the 1997 closure of the local Marine Corps Air Station and plans for the subsequent commercial development of the land, including an unsuccessful bid by neighboring Santa Ana to build a school on the land, part of which is within Santa Ana Unified School District's territory.

In the California State Legislature, Tustin is in the 37th Senate District, represented by Democrat Dave Min and in the 73rd Assembly District, represented by Democrat Cottie Petrie-Norris.

In the United States House of Representatives, Tustin is in California's 40th congressional district, represented by Republican Young Kim.

Primary and secondary education in Tustin and surrounding unincorporated areas is overseen by the Tustin Unified School District. Tustin High School is a California Distinguished School, as is Foothill High School. Arnold O. Beckman High School is in the Best High Schools according to U.S. News & World Report. Tustin High School is also well-known regionally for its strong Model United Nations program.[citation needed] Springfield College, a non-profit, private, higher education institute, is located in the city of Tustin.

The Tustin Police Department is the local law enforcement agency of the city. The department's jurisdiction includes the entire 11.12 square miles (29 km2) of the city of Tustin, as well as the Tustin Legacy development.

Founded in 1928, the Tustin Police Department started with one officer, John Stanton, as "street superintendent", which changed to "chief of police" two months later. Chief Stanton was the only Tustin officer until 1942. At the time of his appointment, there were no police headquarters or stations, and he took calls from his home. The Tustin Police Department had roughly three officers in 1948, twenty years after its founding.