"Rich as Croesus" is an idiom that denotes an immense amount of wealth or opulence. The term originates from the king of Lydia, Croesus, who was considered one of the wealthiest rulers in history. If you are searching for synonyms for the phrase, words such as "filthy rich," "loaded," "wealthy," and "affluent" can be used as equivalent expressions. Other synonymous phrases that can be used include "rolling in dough," "having money to burn," and "living like a king." These terms are commonly used to describe individuals or organizations that have immense financial assets. So, if you want to express the concept of enormous wealth, use these synonyms to convey the message.