The switch, which takes effect in January, is a significant one for Mormons, who since 1980 have been expected to attend all three hours each Sunday to be considered active members of the faith.
The news triggered widespread applause from members, with some posting celebratory memes on social media. It came during the Church of Jesus Christ of Latter-day Saints' twice-yearly conference, where a leader also reaffirmed the faith's opposition to gay marriage and its belief that gender is God-given and eternal.
"The senior leaders of the church have been aware for many years that for some of our precious members, a three-hour Sunday schedule at church can be difficult," said Quentin L. Cook, a member of the Quorum of the Twelve Apostles, leaders who help run the church. "This is particularly true for parents with small children, primary children, elderly members, new converts and others."