Sir William Berkeley (/ˈbɑːrkliː/; 1605 – 9 July 1677) was an English colonial administrator who served as the governor of Virginia from 1660 to 1677. One of the Lords Proprietors of the Province of Carolina, as governor of Virginia he implemented policies that bred dissent among the colonists and sparked Bacon's Rebellion. A favourite of King Charles I, the king first granted him the governorship in 1642. Berkeley was unseated following the execution of Charles I, but his governorship was restored by King Charles II in 1660.

Charles II also named Berkeley one of the eight Lords Proprietors of Carolina, in recognition of his loyalty to the Stuarts during the English Civil War. As governor, Berkeley oversaw the implementation of a policy known as partus sequitur ventrem, which mandated that all babies born to enslaved parents take the legal status of their mother. As proprietor of Green Spring Plantation in James City County, he experimented with activities such as growing silkworms as part of his efforts to expand the tobacco-based economy. He also authored Discourse and View of Virginia, where he argued for diversifying the colony's tobacco economy.

Berkeley was born in 1605 in Bruton, Somersetshire to Maurice Berkeley (died 1617) and Elizabeth Killigrew, of the Bruton branch of the Berkeley family, both of whom held stock in the Virginia Company of London. Referred to as "Will" by his family and friends, he was born in the winter of 1605 into landed gentry. His father died when he was twelve and, though indebted, left Berkeley land in Somerset. His elder brother was John Berkeley, 1st Baron Berkeley of Stratton.

Young Berkeley showed signs of a quick wit and broad learning. His informal education consisted of observing his elders; from them he learned "the moves that governed the larger English society and his privileged place in it". Also, as part of the English country gentry, he was aware of agricultural practices, knowledge which would influence his actions as governor of Virginia.

Though his father died in debt, Berkeley secured a proper education. He entered grammar school at about six or seven years old where he became literate in Latin and English. At eighteen, like the other Berkeley men, he entered Oxford. He began his studies at Queen's College in the footsteps of his forebears, but quickly transferred to St. Edmund Hall, a "throwback to medieval times". He received, though not necessarily completed, a B.A. in fifteen months of his arrival at the Hall.

All undergraduates at St. Edmund Hall received a personal tutor. While the identity of Berkeley's tutor is unsure, his effect upon the boy showed through William's "disciplined intellect and steady appetite for knowledge".

In 1632, he gained a place in the household of Charles I. That position gave him entré into a court literary circle known as "The Wits". Berkeley wrote several plays, one of which — The Lost Lady: A Tragy Comedy — was performed for Charles I and Henrietta Maria and was published in 1638. It is also included in the first and fourth editions of Dodsley's Old Plays, and A Description of Virginia (1663).

Soldiering in the First and Second Bishops' Wars (1639–1640) gained Berkeley a knighthood.