There is significant interest in Korean unification in both North Korea and South Korea. In South Korea, most discussion of unification is based on the assumption that South Korean leaders would control the process because that country's economy and world stature significantly dominate North Korea's. But there are many ways in which unification could occur or be attempted, and each holds vast uncertainties. The literature identifies three possible unification contexts (major war, collapse of North Korea's regime, or peace), across which the author of this report describes nine alternative paths and seven challenges to any potential unification of Korea. He assesses the likelihood of each path and recommends actions that South Korea and the United States could take to achieve a more favorable outcome. The author concludes that South Korea should avoid many of the described paths-especially those involving war or a North Korea-led unification. South Korea needs to develop policies now that would provide most North Korean elites with a friendly outcome from unification. Likely the best path for unification is associated with a collapse of the North Korean regime and involves working with the government that replaces Kim Jong-un to achieve a negotiated unification; such a process would take many years.