William Tailer (February 25, 1675/6 – March 1, 1731/2) was a military officer and politician in the Province of Massachusetts Bay. Born into the wealthy and influential Stoughton family, he twice married into other politically powerful families. He served as lieutenant governor of the province from 1711 until 1716, and again in the early 1730s. During each of these times he was briefly acting governor. He was a political opponent of Governor Joseph Dudley, and was a supporter of a land bank proposal intended to address the province's currency problems. During his first tenure as acting governor he authorized the erection of Boston Light, the earliest lighthouse in what is now the United States.

He was active in the provincial defense, and commanded a regiment in the 1710 siege of Port Royal, the capital of French Acadia, during Queen Anne's War. He was responsible for overseeing the defenses of Boston in the 1720s, and was sent to negotiate with the Iroquois and Abenaki during Dummer's War. Jonathan Belcher, initially a political opponent, later became an ally, and selected him to serve as his lieutenant governor in 1730. Tailer held the post until his death, and was interred in the tomb of his uncle, William Stoughton.