In the Book of Mormon, Ammon(/ˈæm.ʌn/) is a Mulekite descendant and leader of a Nephite expedition from Zarahemla, sent to discover the fate of Zeniff and his people (who had not been in contact for 75 years). Zeniff and his followers left Zarahemla and travelled to Nephi, their ancestral home, which was then in the possession of the Lamanites. This may have contributed to his expedition, not knowing the actual route to Nephi.
Ammon and his men discover the descendants of the people of Zeniff, who had successfully colonized Nephi but were then enslaved by the Lamanites. Zeniff's grandson Limhi rules under the Lamanites and initially imprisons Ammon. Upon learning who Ammon is, he releases him and rejoice his arrival. Ammon teaches the people of Limhi the famous sermon of King Benjamin and helps convert them to the gospel. However, he refuses to baptize the converts, "considering himself an unworthy servant". The reason for his apprehension is not given, and the people wait until they reach Zarahemla to be baptised by Alma the Elder. Ammon, Gideon, and King Limhi conspire to escape from the Lamanites by making the guards drunk. The plan is successful and Ammon escorts them to Zarahemla.