Sir William Pepperrell (June 27, 1696–July 6, 1759) was a British settler and soldier in Colonial Massachusetts. He is most remembered for organizing, financing, and leading the expedition that catured the French establishment at Fortress Louisbourg during King George's War.

William was a native of Kittery, Maine, then part of Massachusetts, and lived there all his life. He studied surveying and navigation before joining his father (a ship-builder and fishing boat owner) in business. He expanded their enterprise to become one of the most properous mercantile houses in New England. He also joined the militia, becomming a captain (1717), major, lieutenant-colonel, and in 1726 colonel of militia.

Pepperrell served in the Massachusetts General Court (1726-1727), and in the Governor's Council (1727-1759), of which for eighteen years he was president. Although not a trained lawyer, he was chief justice of the Court of Common Pleas from 1730 until his death.

In King George's War he proposed the Massachusetts plan for an expedition against the French colony in Nova Scotia. He gathered volunteers, financed and trained the land forces in that campaign. When they sailed in April 1745, he was commander-in-chief of the expedition, supported British squadron under Commodore Peter Warren. They attacked what was then the strongest coastal fortification in America, Fortress Louisbourg. They captured it on June 16 after a six week siege.

He was made a baronet for his exploits in 1746, the only New Englander so honored, and ultimately promoted to Lieutenant General.

In the French and Indian War, he was made a Major General in 1755 responsible for the defence of the Maine and New Hampshire frontier. Throughout that war he was instrumental in raising and training troops for the Massachusetts colony.