Robert Taft Sr., also known as Robert Taft, or Robert Taft I (c. 1640–1725), was the first Taft in the United States and the founder of the American Taft family. The Tafts were said to have been descendants of the Earl of Uxbridge, though there is no reference to this in the appendix to the biography of Alfonso Taft, which has considerable details of the Taft family history from Scotland and the United States.
Robert Taft Sr. was first known to be in Massachusetts in 1675 (or 1678) in Braintree. Another reference listed him from 1669 at Mendon. He lived in Braintree from c. 1675–1680 before moving to Mendon, following King Philip's War. Several of Robert Taft I's children were born at Braintree. The first settlers in Massachusetts were killed at Mendon during the uprising of Native Americans. The Taft family in America developed its roots in Mendon and Uxbridge beginning with Robert Taft Sr. and his wife Sarah (née Simpson). Several of their children were born at Braintree. Robert and Sarah had five children. These are the children born to Robert and Sarah with dates of birth and known locations of their births: Thomas Taft, born 1671, at Mendon, Mass., married Deborah Genery; Robert Taft, born 1674 at Braintree, Mass., married Elizabeth Woodard; Daniel Taft, born 1677 at Braintree, Mass., married Hannah (née ?) and Lydia Chapin; Joseph Taft, born 1680 at Mendon, Mass., married Elizabeth Emerson; Benjamin Taft, born 31 Mar 1684 at Bristol, Mass., married Sarah Thomas and Barsheba Dicke.
The original American Taft homestead was in the part of Mendon, which later became Uxbridge. Robert Taft I bought the deed to the land in 1679. The previous landowner, one Colonel Crown, reportedly left the area during the King Philip's War, and did not return. The home on the land at "Mendham", (old English spelling of Mendon) at present day Uxbridge, was built by Robert Taft (Sr), the first immigrant, in 1680. His son, also called Robert Taft, 2nd, born 1674, was among the first Uxbridge Board of Selectmen in 1727.