The Metropolitan Transit Authority of Harris County is a major public transportation agency based in Houston, Texas, United States. It operates bus, light rail, bus rapid transit, HOV and HOT lanes, and paratransit service in the city as well as most of Harris County. It also operates bus service to two cities in Fort Bend County, and to Conroe in Montgomery County. The Metro headquarters are in the Lee P. Brown Administration Building in Downtown Houston. In 2023, the system had a ridership of 77,189,800, or about 232,800 per weekday as of the fourth quarter of 2023.

Harris County is a county located in the U.S. state of Texas; as of the 2020 census, the population was 4,731,145, making it the most populous county in Texas and the third-most populous county in the United States. Its county seat is Houston, the most populous city in Texas and fourth-most populous city in the United States. The county was founded in 1836 and organized in 1837. It is named for John Richardson Harris, who founded the town of Harrisburg on Buffalo Bayou in 1826. According to the July 2022 census estimate, Harris County's population has shifted to 4,780,913 comprising over 16% of Texas's population. Harris County is included in the nine-county Houston–The Woodlands–Sugar Land metropolitan statistical area, which is the fifth-most populous metropolitan area in the United States.