Recent advances in guanidinium-based receptors are summarized emphasizing the high affinity of the guanidinium moiety towards certain anions in highly competitive aqueous media. Particularly the interaction with multivalent oxoanions such as phosphate, sulfate, chromate, or even pertechnetate is of great interest for recognition. This review summarizes additionally selected developments in guanidine synthesis that are the basis of guanidinium based receptors and functionalized materials with an advanced recognition of certain anions under interfacial aqueous condition.