William King Jackson was born in Washington, D.C., on March 29, 1956. He married Ann Kesler in 1977. They are the parents of eight children.
He attended Brigham Young University for three years. He was awarded a bachelor of science degree from the University of California, Berkeley, and received a doctor of medicine degree from the University of California, San Francisco, in 1983.
He has served in a number of Church callings, including full-time missionary in the Bolivia La Paz Mission, institute teacher, counselor in a district presidency, Sunday School teacher, counselor in a mission presidency, bishop, branch Young Men president, president of the India New Delhi Mission from 2009 to 2012, and Area Seventy and a member of the Third and Eighth Quorums of the Seventy in the Asia and Australia/Pacific Areas from 2003 to 2009.
He is currently serving at Church headquarters in Salt Lake City, Utah, as assistant executive director in the Missionary Department. He is also serving as the chairman of Missionary Health Services.
He worked at McKay-Dee Hospital from 1983 to 1986 for his medical residency and became a certified family physician. He worked as regional medical officer for the U.S. State Department and medical doctor for the Department of the Air Force. At the time of his call as a General Authority, he was serving as medical director of Valley Family Health Care.