The Mark of the Beast is a concept found in the Book of Revelation in the Bible, specifically in Revelation 13:16-18. It is described as a mark that people will receive on their right hand or forehead, allowing them to buy and sell goods. This mark is associated with the Beast, a figure representing opposition to God and His followers. The number associated with the Mark of the Beast is 666, which has been interpreted in various ways throughout history. Many believe it symbolizes imperfection or incompleteness, contrasting with the divine perfection of the number seven. The Mark serves as a warning against allegiance to forces that oppose God.