Sylvester Graham (July 5, 1794 – September 11, 1851) was an American Presbyterian minister and dietary reformer. He was known for his emphasis on vegetarianism, the temperance movement, and eating whole-grain bread. His preaching inspired the graham flour, graham bread, and graham cracker products. Graham is often referred to as the "Father of Vegetarianism" in the United States of America. Graham's lectures caused riots on multiple occasions.

Graham was born July 5, 1794 in Suffield, Connecticut, into a family of 17 children. His father, who was 72 years old at the time of Graham's birth, died when Graham was two years old. His mother was reported to have had mental health issues. During his childhood, Graham lived with various relatives. At one point, he was placed with a relative who operated a tavern, where he worked. Witnessing alcohol abuse during this time reportedly influenced his lifelong opposition to drinking, which was uncommon among his peers.

Graham was frequently in poor health and missed much of his formal education. Before pursuing the ministry, he worked in various occupations, including as a farmhand, cleaner, and teacher. He enrolled at Amherst Academy in his late twenties with the intention of becoming a minister, following the example of his father and grandfather. He withdrew after a year, reportedly due to unfavorable reactions from fellow students to his dramatic speaking style.

Following his departure from school, Graham experienced a period of social isolation and reportedly suffered a nervous breakdown. He relocated to Little Compton, Rhode Island, to recover. While there, he was cared for by a local woman, Sarah Manchester Earl. The two developed a relationship and were married on September 19, 1824. They had three children together: Sarah, Henry, and Caroline.

Graham continued his theological studies independently and, in 1828, began working as an itinerant preacher at the Bound Brook Presbyterian Church in Bound Brook, New Jersey.

In 1830, Graham accepted a position at the Philadelphia Temperance Society. He left six months later to focus on preaching health.

Graham's appointment and conversion to vegetarianism came as the 1826–1837 cholera pandemic was breaking in Europe, and Americans were terrified that it would reach the United States. Accepted medical opinion was that the best way to prevent contracting cholera was to eat plenty of meat, drink port wine, and avoid vegetables. Cholera was widely believed at the time to be a plague or a form of divine punishment.

Unlike most temperance societies of the period, which were typically led by clergy, the Philadelphia Temperance Society was headed by physicians who focused on the health effects of alcohol consumption. While involved with the group, Graham may have encountered two other prominent figures in early American vegetarianism: William Metcalfe, an English minister who founded a vegetarian church in Philadelphia, and William A. Alcott, a Philadelphia physician who wrote extensively on vegetarianism and authored the first American vegetarian cookbook. Graham was largely self-taught in physiology and developed the belief that meat, like alcohol, encouraged gluttony. He argued that both substances degraded the body and soul, with negative consequences for individuals, families, and society.