Wood County is a county in the U.S. state of West Virginia. As of the 2020 census, the population was 84,296, making it West Virginia's fifth-most populous county. Its county seat is Parkersburg. The county was formed in 1798 from the western part of Harrison County and named for James Wood, governor of Virginia from 1796 to 1799.

Wood County is part of the Parkersburg-Vienna, WV Metropolitan Statistical Area.

Settlement in the Ohio Valley was restricted in the years following the French and Indian War. However, the signing of the Treaty of Fort Stanwix and the Treaty of Hard Labor in 1768 cleared the way for the settlement of areas east of the Ohio River, including modern-day Wood County. In the years following the treaties, dozens of settlements were established along the Ohio, Little Kanawha, and Hughes Rivers. By 1775, many immigrants had made settlement and preemption claims in the area that would later constitute Wood County. Most of the earliest settlers were Scotch-Irish who came from southwestern Pennsylvania. One of the earlier settlements in Wood County was established in 1785, when Joseph Wood of New Jersey and four Scottish families settled the area around Belleville.

After surviving a conflict with the local Native American tribes from 1791 to 1795, the area that would become Wood County entered an era of steady but slow expansion and development. Many early settlers had come from the Tidewater Region of Virginia, bringing with them Southern culture and the practice of slavery, using enslaved people to establish plantations. Barbecues and horse racing were common activities among the early inhabitants. Welsh immigrants also came to the area.

Wood County was formed on December 21, 1798, from portions of Harrison County. It was named for the then Governor of Virginia (1796–99), James Wood, formerly a brigadier general in the American Revolutionary War.

Harman Blennerhassett, an Anglo-Irish aristocrat, purchased Blennerhassett Island in 1798, where he built Blennerhassett Mansion. Harman Blennerhassett was known for hosting lavish parties that attracted many high-profile guests. One of the most famous visitors was Aaron Burr. Aaron Burr's relationship with Harman Blennerhassett eventually led to the island being the headquarters for the Burr Conspiracy, with Harman providing financial support and men to Burr.

When word of the Burr Conspiracy leaked out, both Harman Blennerhassett and Aaron Burr fled the island before the Ohio Militia raided it in 1806. Both were later arrested, however the Supreme Court ruled that Burr's plot did not fit the definition of treason. Harman Blennerhassett never regained his wealth after the incident. A fire then burned Blennerhassett Mansion to the ground in 1811, even further complicating the financial issues of the Blennerhassetts.

Harman Blennerhassett tried to regain his fortunes by establishing a cotton plantation in Mississippi, but crop failures doomed the venture. Harman eventually returned to Ireland where he lived off the charity of his relatives. He died in poverty in 1831.