Mandaeans, also known as Mandaean Sabians or simply as Sabians, are an ethnoreligious group who are followers of Mandaeism. They believe that John the Baptist was the final and most important prophet. They may have been among the earliest religious groups to practice baptism, as well as among the earliest adherents of Gnosticism, a belief system of which they are the last surviving representatives today. The Mandaeans were originally native speakers of Mandaic, an Eastern Aramaic language, before they nearly all switched to Mesopotamian Arabic or Persian as their main language.

Mandaeism, sometimes also known as Nasoraeanism or Sabianism, is a Gnostic, monotheistic and ethnic religion with Greek, Iranian, and Jewish influences. Its adherents, the Mandaeans, revere Adam, Abel, Seth, Enos, Noah, Shem, Aram, and especially John the Baptist. Mandaeans consider Adam, Seth, Noah, Shem and John the Baptist prophets, with Adam being the founder of the religion and John being the greatest and final prophet.