路德宗, or Lutheranism, is a major branch of Protestant Christianity that originated in the 16th century. It was founded by 马丁·路德, a German monk, who challenged the practices of the 天主教 Church, particularly the sale of indulgences. His teachings emphasized salvation through faith alone and the authority of the 圣经. Lutheranism spread rapidly across Europe and led to the establishment of various Lutheran churches. It is characterized by its belief in justification by faith, the importance of grace, and the priesthood of all believers. Today, it remains one of the largest Protestant denominations worldwide.