According to the U.S. Census Bureau, the county has a total area of 363.68 square miles (941.9 km), of which 355.75 square miles (921.4 km) is land and 7.93 square miles (20.5 km) (2.18%) is water. It belongs to the southern Piedmont physiographic province.

Most of Gaston County is in the drainage basin of the Catawba River, except for small areas along the western edge of the county which are in the basin of the Broad River. Both the Catawba and Broad Rivers are in the greater Santee River basin. The Catawba forms the eastern border of the county and much of the central part of the county is in the drainage basin of its right tributary, the South Fork Catawba River. The county is located in the Piedmont region of central North Carolina, which consists of gently rolling terrain frequently broken by hills, river and creek valleys, and low, isolated mountain ridges. The highest point in Gaston County is King's Pinnacle, a rocky monadnock which sharply rises over 800 feet (240 m) above the city of Gastonia. King's Pinnacle rises 1,690 feet (520 m) above sea level, and is part of Crowders Mountain State Park.

• Crowders Mountain State Park
• Daniel Stowe Botanical Garden
• Mountain Island Educational State Forest (part)
• Seven Oaks Preserve Trail

• Beaverdam Creek
• Catawba Creek
• Catawba River
• Crowders Creek
• Dutchmans Creek
• Little Beaverdam Creek
• Mountain Island Lake
• Rankin Lake
• South Crowders Creek
• South Fork Catawba River
• South Stanly Creek
• Stanly Creek

• Lincoln County – north
• Mecklenburg County – east
• York County, South Carolina – south
• Cleveland County – west

As of the 2020 census, there were 227,943 people, 85,705 households, and 55,868 families residing in the county.

At the 2004 census estimate, there were 194,459 people, 73,936 households, and 53,307 families residing in the county. The population density was 534 people per square mile (206 people/km). There were 78,842 housing units at an average density of 221 units per square mile (85 units/km). The racial makeup of the county was 83% White, 13.9% Black or African American, 0.3% Native American, 1% Asian, 0% Pacific Islander, 0.3% from other races, and 1% from two or more races. 3.00% of the population were Hispanic or Latino of any race.

There are 92,094 males and 98,271 females in Gaston County. Of these 39,492 are under 15, 23,082 are aged 16–24, 59,096 are aged 25–44, 44,710 are aged between 45–64 and 23,985 are 65 and over. The median age is 36.89 years.

The median income for a household in the county was $39,482, and the median income for a family was $46,271. Males had a median income of $33,542 versus $23,876 for females. The per capita income for the county was $19,225. About 8.30% of families and 10.90% of the population were below the poverty line, including 14.50% of those under age 18 and 11.10% of those age 65 or over.

Gaston County is governed by a seven-member Board of Commissioners. Two members are elected from Gaston Township and one each from the other five townships of Gaston County. They are elected on a partisan basis to four-year staggered terms. Those that file for a particular seat must live in the township. However, the vote is countywide or "at-large."

The offices of Sheriff, District Attorney, Clerk of Superior Court, and Register of Deeds are also elected offices, elected on a countywide, partisan basis. Gaston County currently is divided into forty-six (46) voting precincts.

The county is administered by a full-time professional County Manager. Gaston County is a member of the regional Centralina Council of Governments.

North Carolina has a unified statewide and state-operated court system, called the General Court of Justice. It consists of three divisions: appellate courts, superior courts, and district courts. In Gaston County, there is also a small claims Court.

Small claims court handles civil cases where a plaintiff requests assignment to a magistrate and the amount in controversy is $5,000 or less. There is no jury and usually no lawyers. A person who loses in small claims court may appeal for a trial by jury before a judge in district court. Magistrates are appointed for two-year terms by the senior resident superior court judge upon nomination of the clerk of superior court.

In recent years, voters in most of the county have favored Republicans, though Democrats retain some electoral strength in the city of Gastonia.

Gaston County is served by Amtrak, with a stop in Gastonia. Freight rail service is provided by the Norfolk Southern Railway, CSX and Patriot Rail.

The Norfork Southern main line passes from west to east across the county, passing through Kings Mountain, Bessemer City, Gastonia, Ranlo, Lowell, Cramerton and Belmont. From Gastonia, a branch line leads south to Crowders.

CSX rail lines pass through the northwestern and northeastern corners of Gaston County. In the northwest, a line between Lincolnton and Shelby passes through Cherryville. In the northeast, a line between Lincolnton and Charlotte passes through Stanley and Mount Holly.

Progressive Rail operates state-owned trackage between Gastonia and Mount Holly with a spur extending to Belmont.

Charlotte-Douglas International Airport is a major, full-service airport with passenger flights. It is across the Catawba River in Mecklenburg County in Charlotte.

The city of Gastonia owns and operates Gastonia Municipal Airport, which is a general aviation airport with a single runway, Runway 3/21, an asphalt runway that is 3,779 feet in length.

Piedmont Lithium is a mining company currently in the process of proving economic mineral recovery of lithium in Gaston County. After five years of surface prospecting, the company began drilling many sample cores in 2021 across 2,300 acres (930 ha) of land it owns or has mineral rights to the county proving economic viability of mining lithium for the boom in battery demand to support electric vehicle and other uses.

Public education in Gaston County is administered by the Gaston County Schools public school system. The system is governed by the nine-member Gaston County Board of Education which sets policy and establishes guidelines for school operations. Board members are elected on a nonpartisan, county wide basis, with seven representatives chosen from the six townships and two members selected at-large. Gaston County Schools has 54 public schools, including 9 high schools, 11 middle schools, 32 elementary schools, one alternative school (middle and high school age), and one separate school (Webb Street School in Gastonia) serving students ages 3 to 22 with moderate to severe disabilities.

Gaston County has four charter schools: Community Public Charter School (K-7) in Stanley, Ridgeview Charter School (K–4) in Gastonia, Piedmont Community Charter School (K–12) in Gastonia, and Mountain Island Charter School (K–12) in Mount Holly.

There are two colleges in Gaston County. Gaston College is a community college located in Dallas offering associate degree, Certificate, and Diploma programs. Belmont Abbey College is a Roman Catholic Liberal Arts College located in Belmont.

The Gaston County Public Library has 10 branches spread throughout the county.

Gaston County's most significant natural heritage sites are distributed across the county. They range from Crowders Mountain in the southwest corner to sites east of Stanley and at the mouth of the South Fork Catawba River.

Gaston County has twelve natural heritage sites listed as being of state or regional significance. Six of these are listed because of the presence of the bigleaf magnolia (Magnolia macrophylla). This magnificent plant has the largest simple leaf of any species in the temperate world, and one of the largest flowers. Of the 34 known sites containing bigleaf magnolias in North Carolina, 29 are in Gaston County.

Two sites are important because they provide habitat for the bog turtle (Glyptemys muhlenbergii). The bog turtle is the single most significant rare animal species surviving in Gaston County.

Crowders Mountain State Park is the largest natural heritage site in the county. It covers over 3,000 acres (12 km) of topographically, botanically, and zoologically diverse land. Six natural plant communities are found in the park, and the area supports a diversity of wildlife species. Some animals documented in the park have not been documented elsewhere in the county. A second natural heritage site, Pinnacle Road, has recently been incorporated into the park. This site is most significant for the occurrence of dwarf juniper (Juniperus communis) along its ridgeline.

The Stagecoach Road site is the largest and best preserved granitic outcrop in the county. Its thin soils are dominated by hickory species and it is also home to several smaller species such as Talinum teretifolium (fame flower), Sedum smallii (syn. Diamorpha smallii, Small's sedum), and Hypericum gentianoides (pineweed) that are found only in this type of habitat. A farm site contains an old growth forest dominated by beech, yellow poplar, oaks, and maples - some trees with diameters of nearly 3 feet (0.91 m).

Another 25 sites are listed as being of local significance. Two of these are home to extremely rare plants. Catawba Cove, near the Daniel Stowe Botanical Garden, supports a stand of Schweinitz's sunflower (Helianthus schweinizii), a federally endangered species. The Armstrong Ford site near Belmont is the only place in western North Carolina (and one of only two sites in the state) where magnolia vine (Schisandra glabra) has been found.

The Hoyle Historic Homestead, with notable German-American construction features, is the oldest extant structure in Gaston County. Located on the Dallas-Stanley Highway above the South Fork Catawba River, it was built around 1760 and is listed on the National Register of Historic Places.

The Daniel Stowe Botanical Garden covers 110 acres (0.45 km) in the South Point area of Gaston County, on South New Hope Road.

The Gaston County Museum is located in the town of Dallas, North Carolina.

The Schiele Museum of Natural History is a science museum and planetarium located in Gastonia that features both permanent and touring exhibits.

Crowder's Mountain State Park is noted for its resident raptors and sheer vertical cliffs which drop 150 feet (46 m). From Crowders Mountain, the highest point in Gaston County, views stretch for more than 20 miles (32 km).

The U.S. National Whitewater Center is a recreation and training facility. Set among 1,300 acres (5.3 km) of wooded land along the Catawba River, the multiuse facility has a climbing center, mountain-biking trails and running trails.

Christmas Town USA - McAdenville, North Carolina - Each December, hundreds of thousands of twinkling lights turn this small mill town into a spectacular holiday display. Visitors stroll down Main Street surrounded by the sights and sounds of Christmas.

Spencer Mountain, which is located in central Gaston County, is the site of the old WBTV television transmitter. It was from this site that the first commercial television signal in North Carolina was broadcast, when WBTV signed on the air in 1949. The tower remains on the mountain today, but is no longer in use as WBTV's primary transmitter. It is used by NWS for its NOAA Weather Radio transmission signal.

• Belmont
• Bessemer City
• Cherryville
• Gastonia (county seat and largest community)
• Kings Mountain (mostly in Cleveland County)
• Lowell
• Mount Holly

Townships are administrative divisions of unincorporated county land and do not have any government function.

• List of counties in North Carolina
• National Register of Historic Places listings in Gaston County, North Carolina

• McCorkle, Mac; Salzberg, Rachel (January 2022), The Democrats’ Countrypolitan Problem in North Carolina: Progressive Challenge and Opportunity, Duke University Polis: Center for Politics

• "Gaston County", Branson's North Carolina Business Directory...1867-68, p. 45 – via hathitrust.org
• "Gaston County", Branson's North Carolina Business Directory 1896, p. 284 – via archive.org
• "Gaston County", North Carolina Year Book and Business Directory, 1916, Raleigh, N.C.: News and Observer Publishing Company – via hathitrust.org

Wikimedia Commons has media related to Gaston County, North Carolina.

• Geographic data related to Gaston County, North Carolina at OpenStreetMap
• Official website
• Gaston Regional Chamber of Commerce
• Gaston County Schools official website
• NCGenWeb Gaston County, genealogy resources for the county