Hacienda Heights (pronunciationⓘ) is an unincorporated suburban community in Los Angeles County, California, United States. As of the 2020 census, the community had a total population of 54,191, up from 54,038 at the 2010 census. For statistical purposes, the Census Bureau has defined Hacienda Heights as a census designated place (CDP). It is the second largest CDP in Los Angeles County by area, behind Topanga, and the county's fourth largest CDP by population.

Hacienda Heights sits on land that was originally part of Rancho La Puente. During Spanish rule, the land around Hacienda Heights was operated by the nearby Mission San Gabriel Arcángel in San Gabriel. The Rancho was eventually acquired by John A. Rowland and William Workman in 1845 via a Mexican land grant, and eventually acquired by Elias "Lucky" Baldwin in the mid-1870s. In 1912, his descendant, Anita Baldwin, sold the property to Edwin Hart and Jet Torrance. In 1913 the pair subdivided the area and named it North Whittier Heights, which became known for avocado, citrus and walnut orchards. However, from the Great Depression era to the early 1940s, citrus growing became unprofitable because of pests and diseases, setting the impetus for the area's transformation into a suburb.

Accelerating in the 1950s, suburban residential development transformed Hacienda Heights into a residential or bedroom community. In 1960, the Hacienda Heights Branch of the Los Angeles County Public Library opened. The following year, in 1961, the area was renamed Hacienda Heights. In 1964, the local newspaper, the Hacienda Heights Highlander, was established.

The hills surrounding Hacienda Heights have a history of brush fires, especially in 1978, 1989, and 2020.

Hacienda Heights is in the eastern San Gabriel Valley bordering City of Industry to the North, Whittier to the West, La Habra Heights to the South, and Rowland Heights to the East along the Pomona Freeway - Route 60. Hacienda Heights is a predominantly residential neighborhood.

According to the United States Census Bureau, the community has a total area of 11.2 square miles (29 km2), of which only 0.06% is water.

Hacienda Heights also has the Puente Hills forming its 'green belt' southern border and much of its western border. The highest point is Workman Hill at 1,391 feet (424 m). Coyotes are common concern among residents.

The 2010 United States Census reported that Hacienda Heights had a population of 54,038. The population density was 4,832.4 inhabitants per square mile (1,865.8/km2). The racial makeup of Hacienda Heights was 38% White (12.6% Non-Hispanic White), 1.1% African American, 0.3% Native American, 39.3% Asian, 0.3% Pacific Islander, and 2.8% from two or more races. Hispanic or Latino of any race were 46%.

The census reported that 53,928 people (99.8% of the population) lived in households, 70 (0.1%) lived in non-institutionalized group quarters, and 40 (0.1%) were institutionalized.

There were 16,193 households, out of which 6,185 (38.2%) had children under the age of 18 living in them, 10,151 (62.7%) were opposite-sex married couples living together, 2,331 (14.4%) had a female householder with no husband present, 1,024 (6.3%) had a male householder with no wife present. There were 555 (3.4%) unmarried opposite-sex partnerships, and 93 (0.6%) same-sex married couples or partnerships. 2,111 households (13.0%) were made up of individuals, and 1,047 (6.5%) had someone living alone who was 65 years of age or older. The average household size was 3.33. There were 13,506 families (83.4% of all households); the average family size was 3.59.

The CDP population contained 11,864 people (22.0%) under the age of 18, 5,184 people (9.6%) aged 18 to 24, 13,597 people (25.2%) aged 25 to 44, 15,071 people (27.9%) aged 45 to 64, and 8,322 people (15.4%) who were 65 years of age or older. The median age was 40.1 years. For every 100 females there were 94.8 males. For every 100 females age 18 and over, there were 92.4 males.

There were 16,650 housing units at an average density of 1,488.9 per square mile (574.9/km2), of which 12,720 (78.6%) were owner-occupied, and 3,473 (21.4%) were occupied by renters. The homeowner vacancy rate was 1.0%; the rental vacancy rate was 3.6%. 42,189 people (78.1% of the population) lived in owner-occupied housing units and 11,739 people (21.7%) lived in rental housing units. Median value of owner-occupied housing units, 2013–2017 was $545,400 with medium gross rent of $1,734.

West of Hacienda Heights is the former Puente Hills Landfill, which was at one time the largest landfill in the U.S. until its closure in 2013. It is now used as a gas-to-energy facility, as well as part of the Puente Hills Habitat Authority.

The "Puente Hills Landfill Native Habitat Preservation Authority" supports public enjoyment and access of the nearby parkland in the Puente Hills. Some of the hiking trails they offer are Hacienda Hills, Sycamore Canyon, Turnbull Canyon and Hellman Park.

Hsi Lai Temple (meaning "Coming West"), a branch of Fo Guang Shan of Taiwan, is the largest Buddhist temple in North America. The temple was completed in 1988 and encompasses 15 acres (61,000 m2) and a floor area of 102,432 sq ft (9,516 m2). The temple's Ming dynasty (1368–1644) and Qing dynasty (1644–1911) architecture is faithful to the traditional style of buildings, Chinese gardens, and statuary of ancient Chinese monasteries. Hsi Lai was built to serve as a spiritual and cultural center for Buddhism and Chinese culture.

In the state senate, Hacienda Heights is located in the 30th Senate District, represented by Democrat Bob Archuleta.

In the California State Assembly it is located in the 56th Assembly District, represented by Democrat Lisa Calderon.

Federally, Hacienda Heights is located in California's 38th congressional district, represented by Democrat Linda Sánchez.

The Los Angeles County Sheriff's Department operates the Industry Station in the City of Industry, serving Hacienda Heights.

The Los Angeles County Department of Health Services operates the Pomona Health Center in Pomona, serving Hacienda Heights.

In 2003, voters were asked to decide whether the community should incorporate and become a city. Proponents argued that a new city would be able to better control development and provide increased police and fire service, while opponents argued that the new city would increase taxes and redevelop residential neighborhoods for revenue-generating businesses. Most of the prime commercial land had already been annexed by the City of Industry to escape taxes levied by the County on unincorporated areas. Ultimately the measure failed by about a 2-1 margin.

The city is served by the Hacienda La Puente Unified School District.

Glenelder Elementary School was merged with Cedarlane and Shadybend was closed down, too.

Since 1966, St. John Vianney Catholic Church in Hacienda Heights has hosted a carnival event called "Early California Days", (also known as 'Harvest in the Heights') usually held for a week each summer. The festivities consists of rides, games, food, music and a grand raffle with cash prizes.