Polymers have played a crucial role in advancing drug delivery technology by enabling controlled release of therapeutic agents in constant doses over long periods, cyclic dosing, and tunable release of both hydrophilic and hydrophobic drugs. The field has grown significantly, driven by innovations in chemical engineering. Modern drug delivery relies on the rational design of polymers tailored for specific cargo and engineered for distinct biological functions. This review highlights fundamental drug delivery systems, their mathematical foundations, and physiological barriers to drug delivery. It discusses stimuli-responsive polymer systems and polymer therapeutics, such as polymer-protein and polymer-drug conjugates. Recent developments in polymers capable of molecular recognition or directing intracellular delivery are surveyed to illustrate areas of research advancing drug delivery. Polymers are used in drug delivery systems to provide controlled release, sustained delivery, and targeted delivery. Diffusion-controlled systems rely on the diffusion of drugs through a polymer matrix, while solvent-activated systems respond to changes in the surrounding environment. Biodegradable systems are designed to degrade in the body, releasing drugs over time. These systems are important for drug delivery because they can be tailored to specific therapeutic needs and can be designed to release drugs in a controlled manner. Responsive polymers, such as temperature- and pH-responsive polymers, are used in drug delivery to control the release of drugs in response to specific physiological conditions. These polymers can be designed to release drugs in response to changes in temperature, pH, or other stimuli. Redox-responsive polymers are also being explored for drug delivery, as they can respond to changes in the redox environment within the body. Polymer therapeutics, such as polymer-drug conjugates and polymer-protein conjugates, are used in drug delivery to improve the pharmacokinetic and pharmacodynamic properties of drugs. These conjugates can be designed to target specific tissues or cells, improving the efficacy of drug delivery. The review also discusses the applications and examples of these polymer therapeutics, including their use in cancer therapy and other diseases. The review concludes by emphasizing the importance of polymer therapeutics in drug delivery and the need for further research to develop more effective and targeted drug delivery systems.Polymers have played a crucial role in advancing drug delivery technology by enabling controlled release of therapeutic agents in constant doses over long periods, cyclic dosing, and tunable release of both hydrophilic and hydrophobic drugs. The field has grown significantly, driven by innovations in chemical engineering. Modern drug delivery relies on the rational design of polymers tailored for specific cargo and engineered for distinct biological functions. This review highlights fundamental drug delivery systems, their mathematical foundations, and physiological barriers to drug delivery. It discusses stimuli-responsive polymer systems and polymer therapeutics, such as polymer-protein and polymer-drug conjugates. Recent developments in polymers capable of molecular recognition or directing intracellular delivery are surveyed to illustrate areas of research advancing drug delivery. Polymers are used in drug delivery systems to provide controlled release, sustained delivery, and targeted delivery. Diffusion-controlled systems rely on the diffusion of drugs through a polymer matrix, while solvent-activated systems respond to changes in the surrounding environment. Biodegradable systems are designed to degrade in the body, releasing drugs over time. These systems are important for drug delivery because they can be tailored to specific therapeutic needs and can be designed to release drugs in a controlled manner. Responsive polymers, such as temperature- and pH-responsive polymers, are used in drug delivery to control the release of drugs in response to specific physiological conditions. These polymers can be designed to release drugs in response to changes in temperature, pH, or other stimuli. Redox-responsive polymers are also being explored for drug delivery, as they can respond to changes in the redox environment within the body. Polymer therapeutics, such as polymer-drug conjugates and polymer-protein conjugates, are used in drug delivery to improve the pharmacokinetic and pharmacodynamic properties of drugs. These conjugates can be designed to target specific tissues or cells, improving the efficacy of drug delivery. The review also discusses the applications and examples of these polymer therapeutics, including their use in cancer therapy and other diseases. The review concludes by emphasizing the importance of polymer therapeutics in drug delivery and the need for further research to develop more effective and targeted drug delivery systems.