For others with similar names, see: William Alexander (disambiguation).

Sir William Alexander, Earl of Stirling (c.1570–1640) was a Scotsman who was an early developer of British colonization of Nova Scotia. He was a courtier in Scotland before its throne was joined with that of England to create the United Kingdom, and was knighted in 1614. In 1621 King James I granted him a royal charter appointing him governor of a vast territory in North America which was erected into a lordship and barony of Nova Scotia; the area now know as Nova Scotia, New Brunswick, and part of the northern United States. The creation of Baronets of Nova Scotia was used to settle the plantation of the new province.

Alexander was an active promoter of his New Scotland and brought many British settlers to the maritimes. He was appointed Secretary for Scotland in 1626 and held that office for the rest of his life. In 1630, King Charles rewarded his service by creating him Viscount Stirling and in 1633 he became Earl of Stirling.

Lord Stirling’s efforts at colonization were less successful, at least from a monetary standpoint. He spent his fortune, and when the maritimes were returned to France in 1632, it was lost. He spent his later years with limited means, and died in London on September 12, 1640.