Over the past decades, peptides that structurally and/or functionally mimic HIV proteins have significantly contributed to the molecular and structural understanding of HIV live cycle and infection pathways. Moreover, such peptides are promising candidates for therapeutic and preventive anti-HIV strategies, because they can be used as inhibitors of virus–host interactions that are essential for virus entry and replication. Furthermore, peptides that mimic the binding sites of HIV proteins for their host cell receptors are immunogen candidates for new vaccine strategies. This aspect is of particular importance in light of the persisting neutralizing antibody problem in the field of HIV vaccine development, whose solution will clearly require innovative strategies in the immunogen design.