Petrolia is a city in Clay County, Texas, United States. It is part of the Wichita Falls, Texas Metropolitan Statistical Area. The population was 514 at the 2020 census, down from 686 at the 2010 census.

Petrolia is located in northern Clay County. Texas State Highway 79 passes through the center of town, leading southwest 17 miles (27 km) to Wichita Falls and northeast 18 miles (29 km) to Waurika, Oklahoma. Texas State Highway 148 leads south from the center of Petrolia 14 miles (23 km) to Henrietta, the Clay County seat.

According to the United States Census Bureau, Petrolia has a total area of 0.73 square miles (1.9 km), all land.

Historical population

Census	Pop.	Note	%±
1910	517		—
1920	914		76.8%
1930	806		−11.8%
1940	597		−25.9%
1950	606		1.5%
1960	631		4.1%
1970	584		−7.4%
1980	755		29.3%
1990	762		0.9%
2000	782		2.6%
2010	686		−12.3%
2020	514		−25.1%
U.S. Decennial Census 2020 Census

As of the census of 2000, there were 782 people, 305 households, and 215 families residing in the city. The population density was 1,051.1 inhabitants per square mile (405.8/km). There were 338 housing units at an average density of 454.3 per square mile (175.4/km). The racial makeup of the city was 94.88% White, 0.77% African American, 1.41% Native American, 1.15% from other races, and 1.79% from two or more races. Hispanic or Latino of any race were 3.96% of the population.

There were 305 households, out of which 32.1% had children under the age of 18 living with them, 53.8% were married couples living together, 13.1% had a female householder with no husband present, and 29.2% were non-families. 26.6% of all households were made up of individuals, and 13.8% had someone living alone who was 65 years of age or older. The average household size was 2.56 and the average family size was 3.07.

In the city, the population was spread out, with 26.9% under the age of 18, 9.5% from 18 to 24, 26.9% from 25 to 44, 22.1% from 45 to 64, and 14.7% who were 65 years of age or older. The median age was 36 years. For every 100 females, there were 77.7 males. For every 100 females age 18 and over, there were 78.2 males.

The median income for a household in the city was $27,386, and the median income for a family was $31,250. Males had a median income of $26,136 versus $16,731 for females. The per capita income for the city was $12,825. About 16.6% of families and 17.6% of the population were below the poverty line, including 20.2% of those under age 18 and 20.5% of those age 65 or over.

• Reed Hadley, actor on Racket Squad and The Public Defender; born in Petrolia in 1911
• David Nelson, NFL football player for the New York Jets

The city is served by the Petrolia Independent School District and is home to the Petrolia High School Pirates.

• See historic photos of Petrolia from the Clay County Historical Society, hosted by the Portal to Texas History