SEOUL—South Korea’s Constitutional Court ousted President Yoon Suk Yeol over his short-lived declaration of martial law, clearing the way for a snap vote to elect a new president who will contend with deep divisions at home and rising friction with the U.

South Korea’s Constitutional Court removed impeached President Yoon Suk Yeol from office on Friday, four months after he threw South Korean politics into turmoil by declaring martial law and sending troops to parliament in an ill-fated effort to break through legislative gridlock.