Cotton Mather (; February 12, 1663 – February 13, 1728) was a New England Puritan clergyman and writer. Educated at Harvard College, in 1685 he joined his father Increase as minister of the Congregationalist Old North Meeting House of Boston, where he continued to preach for the rest of his life.

A major intellectual and public figure in English-speaking colonial America, Cotton Mather helped lead the successful revolt of 1689 against Sir Edmund Andros, the governor imposed on New England by King James II. Mather's subsequent involvement in the Salem witch trials of 1692–1693, which he defended in the book Wonders of the Invisible World (1693), attracted intense controversy in his own day and has negatively affected his historical reputation. As a historian of colonial New England, Mather is noted for his Magnalia Christi Americana (1702).

Personally and intellectually committed to the waning social and religious orders in New England, Cotton Mather unsuccessfully sought the presidency of Harvard College, an office that had been held by his father Increase, another significant Puritan clergyman and intellectual. After 1702, Cotton Mather clashed with Joseph Dudley, the governor of the Province of Massachusetts Bay, whom Mather attempted unsuccessfully to drive out of power. Mather championed the new Yale College as an intellectual bulwark of Puritanism in New England. He corresponded extensively with European intellectuals and received an honorary Doctor of Divinity degree from the University of Glasgow in 1710.

A promoter of the new experimental science in America, Cotton Mather carried out original research on plant hybridization and on the use of inoculation as a means of preventing smallpox contagion. He dispatched many reports on scientific matters to the Royal Society of London, which elected him as a fellow in 1713. Mather's promotion of inoculation against smallpox, which he had learned about from an African named Onesimus whom Mather held as a slave, caused violent controversy in Boston during the outbreak of 1721. Scientist and US founding father Benjamin Franklin, who as a young Bostonian had opposed the old Puritan order represented by Mather and participated in the anti-inoculation campaign, later described Mather's book Bonifacius, or Essays to Do Good (1710) as a major influence on his life.