The Seventh-day Adventist Church is an Adventist Protestant Christian denomination which is distinguished by its observance of Saturday, the seventh day of the week in Christian (Gregorian) and the Hebrew calendar, as the Sabbath, and its emphasis on the imminent Second Coming (advent) of Jesus Christ. The denomination grew out of the Millerite movement in the United States during the mid-19th century and it was formally established in 1863. Among its co-founders was Ellen G. White, whose extensive writings are still held in high regard by the church. Much of the theology of the Seventh-day Adventist Church corresponds to common evangelical Christian teachings, such as the Trinity and the infallibility of Scripture. Distinctive post-tribulation teachings include the unconscious state of the dead and the doctrine of an investigative judgment. The church is known for its emphasis on diet and health, including adhering to Kosher food laws, advocating vegetarianism, and its holistic understanding of the person. It is likewise known for its promotion of religious liberty, and its conservative principles and lifestyle.

The world church is governed by a General Conference of Seventh-day Adventists, with smaller regions administered by divisions, union conferences, and local conferences. The Seventh-day Adventist Church is currently "one of the fastest-growing and most widespread churches worldwide", with a worldwide baptized membership of over 21 million people, and 25 million adherents. As of May 2007, it was the twelfth-largest religious body in the world, and the sixth-largest highly international religious body. It is ethnically and culturally diverse, and maintains a missionary presence in over 215 countries and territories. The church operates over 7,500 schools including over 100 post-secondary institutions, numerous hospitals, and publishing houses worldwide, as well as a humanitarian aid organization known as the Adventist Development and Relief Agency (ADRA).