There are several synonyms for the phrase "prior to" that can be used to convey the same meaning. One alternative is "before," which is a common and straightforward replacement. Another synonym is "previously," which can be used to describe something that happened earlier than another event. "Formerly" is another option, which suggests that something was in place or existed before the current situation. "Earlier" is a concise synonym for "prior to," and "preceding" can be used in situations where there are a series of events. Overall, there are various synonyms for "prior to" that can add variety and clarity to your communication.