Over the past six decades, the alliance between the Republic of Korea and the United States has become one of the most successful military alliances in history. Numerous strategic changes are anticipated in Northeast Asia over the coming years, including the risk of a military attack by North Korea and a shift in the balance of power. Among multiple factors that contribute to the success of an alliance, one key factor is sharing a common vision of the future since sharing this is crucial to enhance the trust shared today and to reinforce the alliance’s capability to respond effectively to any new challenges that may arise. This paper seeks to offer a vision for the ROK-U.S. alliance and make suggestions on how the alliance can develop and improve in the future by trying to forecast changes in the security circumstances surrounding the Korean Peninsula and Northeast Asia until around 2030. As a result, this paper finds the fact that maintaining the ROK-U.S. alliance is the optimal choice for both countries until 2030, despite the various strategic changes in Northeast Asia, including a possible national reunification of the Korean Peninsula and presents a long-term vision for the ROK-U.S. alliance based on this fact and some implementation strategies for this vision.