I'm a U.S. citizen, and I'm engaged to a foreign national. Can we get married in the U.S. without obtaining a K-1 visa?

If your fiancé(e) is already in the U.S. on a valid visa, you may be able to get married in the U.S. without obtaining a K-1 visa

If your fiancé(e) is outside the U.S., you'll need to apply for a K-1 visa, also known as a fiancé(e) visa, to bring them to the U.S. for the purpose of getting married