2020 census
As of the 2020 United States census, there were 160,368 people, 57,835 households, and 34,816 families residing in the parish.
2000 census
As of the census of 2000, there were 147,250 people, 55,216 households, and 38,319 families residing in the parish. The population density was 241 people per square mile (93/km2). There were 60,154 housing units at an average density of 98 per square mile (38/km2). The racial makeup of the parish was 64.48% White, 33.63% Black or African American, 0.23% Native American, 0.64% Asian, 0.03% Pacific Islander, 0.33% from other races, and 0.67% from two or more races. 1.19% of the population were Hispanic or Latino of any race.
There were 55,216 households, out of which 34.20% had children under the age of 18 living with them, 47.70% were married couples living together, 17.90% had a female householder with no husband present, and 30.60% were non-families. 25.80% of all households were made up of individuals, and 9.30% had someone living alone who was 65 years of age or older. The average household size was 2.58 and the average family size was 3.12.
In the parish the population was spread out, with 27.90% under the age of 18, 12.00% from 18 to 24, 27.90% from 25 to 44, 20.30% from 45 to 64, and 11.80% who were 65 years of age or older. The median age was 32 years. For every 100 females there were 89.30 males. For every 100 females age 18 and over, there were 84.50 males.
The median income for a household in the parish was $32,047, and the median income for a family was $40,206. Males had a median income of $31,616 versus $23,139 for females. The per capita income for the parish was $17,084. About 15.80% of families and 20.70% of the population were below the poverty line, including 29.70% of those under age 18 and 15.80% of those age 65 or over.
Economy
The top employers in the parish, according to the North Louisiana Economic Partnership, are:
Politics
Education
Ouachita Parish School Board serves areas outside of the City of Monroe with primary and secondary schools. Monroe City School System serves areas within Monroe.
Monroe is also the home of the University of Louisiana at Monroe.
Media
A documentary entitled The Gift of the Ouachita by filmmaker George C. Brian (1919–2007), head of the Division of Theater and Drama at the University of Louisiana at Monroe is a history of Monroe as the "gift of the Ouachita River".
National Guard
1022nd Engineer Company (Vertical) of the 527th Engineer Battalion of the 225th Engineer Brigade is located in West Monroe, Louisiana. 528th Engineer Battalion (To the Very End) also part of the 225th Engineer Brigade is headquartered in Monroe.
Communities
thumb|250px|Map of Ouachita Parish, Louisiana With Municipal Labels
Cities
Monroe (parish seat and largest municipality)
West Monroe
Towns
Richwood
Sterlington
Unincorporated areas
Census-designated places
Bawcomville
Brownsville
Calhoun
Claiborne
Lakeshore
Swartz
Other unincorporated communities
Bosco
Fairbanks
Pine Grove
Wham
Notable people
Joseph A. Biedenharn
Evelyn Blackmon
Samuel B. Fuller
James D. Halsell
Dixon Hearne
Alton Hardy Howard
Newt V. Mills
Mike Walsworth
Willie Robertson
Phil Robertson
Si Robertson
Jase Robertson
Edwin Francis Jemison