Fort Bend County is a county located in the U.S. state of Texas. The county was founded on December 29, 1837, and organized the next year. It is named for a blockhouse at a bend of the Brazos River. The community developed around the fort in early days. The county seat is Richmond. The largest city located entirely within the county borders is Sugar Land. The largest city by population in the county is Houston, but most of Houston's population is located in neighboring Harris County.

Fort Bend County is included in the Houston–The Woodlands–Sugar Land metropolitan statistical area. As of the 2020 census, its population was 822,779, making it the state's eighth-most populous county, and was estimated to be 958,434 in 2024. In 2017, Forbes ranked it the fifth-fastest growing county in the United States.

Before European settlement, the area was inhabited by Karankawa Indians. Spanish colonists generally did not reach the area during their colonization, settling more in South Texas.

After Mexico achieved independence from Spain, Anglo-Americans started entering from the east. In 1822, a group of Stephen F. Austin's colonists, headed by William Travis, built a fort at the present site of Richmond. The fort was called Fort Bend because it was built in the bend of the Brazos River. The city of Richmond was incorporated under the Republic of Texas, along with 19 other towns, in 1837. Fort Bend County was created from parts of Austin, Harris, and Brazoria Counties in 1838.

Fort Bend developed a plantation economy based on cotton as the commodity crop. Planters had numerous African-American slaves as laborers. By the 1850s, Fort Bend was one of six majority-black counties in Texas. In 1860, the slave population totaled 4,127, more than twice that of the 2,016 whites. Few free Blacks lived there, as Texas refused them entry.

While the area began to attract White immigrants in the late 19th century, it remained majority-Black during and after Reconstruction. Whites endeavored to control freedmen and their descendants through violence and intimidation. Freedmen and their sympathizers supported the Republican Party because of emancipation, electing their candidates to office. The state legislature was still predominately White. By the 1880s, most White residents belonged to the Democratic Party. Factional tensions were fierce, as political elements split largely along racial lines. The Jaybirds, representing the majority of the Whites, struggled to regain control from the Woodpeckers, who were made up of some Whites who were consistently elected to office by the majority of African Americans, as several had served as Republican officials during Reconstruction.

Fort Bend County was the site of the Jaybird–Woodpecker War in 1888–89. After a few murders were committed, the political feud culminated in a gun battle at the courthouse on August 16, 1889, when several more people were killed and the Woodpeckers were routed from the county seat.

Governor Lawrence Sullivan Ross sent in militia forces and declared martial law. With his support, the Jaybirds ordered a list of certain Blacks and Woodpecker officials out of the county, overthrowing the local government. The Jaybirds took over county offices and established a "White-only pre-primary", disenfranchising African Americans from the only competitive contests in the county. This device lasted until 1950, when Willie Melton and Arizona Fleming won a lawsuit against the practice in United States District Court, though it was overturned on appeal. In 1953, they ultimately won their suit when the Supreme Court of the United States declared the Jaybird primary unconstitutional in Terry v. Adams, the last of the White primary cases.