Aptamers,which can be generated via systematic evolution of ligands by exponential enrichment(SELEX),are superior ligands for molecular recognition due to their high selectivity and affinity.The interest in the use of aptamers as ligands for targeted drug delivery has been increasing for their unique advantages.Based on their different compositions and preparation methods,aptamer-functionalized targeted drug delivery systems can be divided into two main categories: aptamer-drug delivery systems and aptamer-nanomaterial delivery systems.In this review,we not only summarize recent progress in aptamer selection and the application of aptamers in these targeted drug delivery systems but also discuss the advantages,challenges and new perspectives associated with these delivery systems.