药物设计（英语：Drug design），又称理性药物设计（rational drug design），或理性设计（rational design），根据对于生物目标（Biological target）的现有知识，去寻找与发明出新型药物的过程。药物设计根据有机体小分子物质，如蛋白质，的化学结构、电价与形状等，来设计出可能达到效果的新型化学药物。使用电脑分子建构技术，来进行药物设计，称为电脑辅助药物设计（computer-aided drug design）。根据对于生物目标的化学结构来进行设计，称为结构药物设计（structure-based drug design）。

Drug design, often referred to as rational drug design or simply rational design, is the inventive process of finding new medications based on the knowledge of a biological target. The drug is most commonly an organic small molecule that activates or inhibits the function of a biomolecule such as a protein, which in turn results in a therapeutic benefit to the patient. In the most basic sense, drug design involves the design of molecules that are complementary in shape and charge to the biomolecular target with which they interact and therefore will bind to it. Drug design frequently but not necessarily relies on computer modeling techniques. This type of modeling is sometimes referred to as computer-aided drug design. Finally, drug design that relies on the knowledge of the three-dimensional structure of the biomolecular target is known as structure-based drug design. In addition to small molecules, biopharmaceuticals and especially therapeutic antibodies are an increasingly important class of drugs and computational methods for improving the affinity, selectivity, and stability of these protein-based therapeutics have also been developed.