Missionaries of The Church of Jesus Christ of Latter-day Saints (LDS Church)—widely known as Mormon missionaries—are volunteer representatives of the LDS Church who engage variously in proselytizing, church service, humanitarian aid, and community service. Mormon missionaries may serve on a full- or part-time basis, depending on the assignment, and are organized geographically into missions. The mission assignment could be to any one of the 418 missions organized worldwide.
The LDS Church is one of the most active modern practitioners of missionary work, reporting that it had over 74,000 full-time missionaries worldwide at the end of 2015 (as well as nearly 32,000 part-time church-service missionaries). Most full-time Mormon missionaries are single young men and women in their late teens and early twenties and older couples no longer with children in the home. Missionaries are often assigned to serve far from their homes, including in other countries. Many missionaries learn a new language at a missionary training center as part of their assignment. Missions typically last two years for males, 18 months for females, and 6 to 18 months for older couples. The LDS Church strongly encourages, but does not require, missionary service for young men. All Mormon missionaries serve voluntarily and do not receive a salary for their work; they typically finance missions themselves or with assistance from family or other church members. Many Latter-day Saints save money during their teenage years to cover their mission expenses.
Throughout the church's history, over one million missionaries have been sent on missions.
LDS Church president Spencer W. Kimball said, "Every young man should fill a mission". Completing a mission is often described as a rite of passage for a young Latter-day Saint. The phrase "the best two years of my life" is a common cliché among returned missionaries when describing their experience. Although Gordon B. Hinckley had suggested that a mission is not to be a rite of passage, this cultural aspect remains. With the usual starting age of 18–20, a mission provides a clear event or marker for the traditional age of adulthood, but is not necessary for continuance in church membership. For many it is a variation on tithing—which customarily involves the donating of ten percent of income to the church—by donating ten percent of the prospective missionary's life to the service of the church.