In the Book of Mormon, the Lamanites (/ˈleɪmənaɪt/) are one of the four peoples (along with the Jaredites, the Mulekites, and the Nephites) described as having settled in the ancient Americas. The Lamanites also play a role in the prophecies and revelations of the Doctrine and Covenants, another sacred text in the Latter Day Saint movement.

In the Book of Mormon's narrative, the Lamanites begin as wicked rivals to the more righteous Nephites, but when the Nephite civilization became decadent, it lost divine favor and was destroyed by the Lamanites. Latter Day Saints have historically associated Lamanites with present-day Native American cultures.

According to the Book of Mormon, the family of Lehi, described as a wealthy Hebrew prophet, the family of Ishmael, and Zoram traveled from the Middle East to the Americas by boat in around 600 BC. In his dying blessings to his children, Lehi assigns tribes to his descendants, usually named after the son whose family made up the tribe: Nephites, Jacobites, Josephites, Zoramites, Lamanites, Lemuelites, and Ishmaelites after Nephi, Joseph, Zoram, Laman, and Lemuel. Lehi's son Sam is included in the Nephites, his sons-in-law are presumably included together in the Ishmaelites, and Zoram was not Lehi's son, but his family travelled with Lehi's family. In 2 Nephi 5, the narrative divides the people into Nephites and Lamanites; in his book The Testimony of Two Nations, Michael Austin interprets these as categories of convenience for the sake of the narrative, similar to how the twelve tribes of Israel are divided into the Kingdom of Israel and the Kingdom of Judah in the Old Testament.

After the two groups separated from each other, the rebellious Lamanites were cursed and "cut off from the presence of the Lord." They received a "skin of blackness" so they would "not be enticing" to the Nephites. Centuries later, the narrative in the Book of Alma still describes the skin of the Lamanites as "dark."

The Book of Mormon describes the animosity the Lamanite people held toward the Nephites. The Lamanites believed they were "driven out of the land of Jerusalem because of the iniquities of their fathers" and were wronged by Nephi and so swore vengeance against his descendants. The Lamanites taught their children to have "eternal hatred" towards the Nephites, and "that they should murder them, and that they should rob and plunder them, and do all they could to destroy them."

After the two groups warred for centuries, the narrative states that Jesus Christ appeared to the more righteous Nephites and the Lamanites, who, by then, had converted in large numbers to righteousness before God. Soon after his visit, the Lamanites and Nephites merged into one nation and co-existed for two centuries in peace. The Book of Mormon further recounts, "There were no robbers, nor murderers, neither were there Lamanites, nor any manner of -ites; but they were in one, the children of Christ, and heirs to the kingdom of God."

However, 84 years after the coming of Christ, "a small part of the people who had revolted from the church" started calling themselves Lamanites again. Those who remained were again identified as Nephites, but both groups were reported to have fallen into apostasy. The reestablished Lamanites and Nephites were largely distinguished by ideological choices rather than by previous ethnic distinctions. The Book of Mormon recounts a series of large battles over two centuries, ending with the extermination of the Nephites by the Lamanites.

The Doctrine and Covenants is composed of writings that adherents in the Latter Day Saint movement believe to be revelations from God. It is considered scripture in the sacred text of the Latter Day Saint movement and says that God called Oliver Cowdery (D&C 28:8) and later Peter Whitmer and Parley P. Pratt (D&C 32:1–2) to teach the gospel to the Lamanites. Cowdery is given the power to build up God's church among them (D&C 30:6). The men believed that God was referring to the Native Americans and began teaching among the Lenape.