In recent years, understanding ways to improve the value and impact of heterocycles, in drug discovery and medicinal chemistry has increased with understanding of the multitude ways this fragment can influence properties. This chapter defines heterocycles as aromatic and non-aromatic rings containing one or more non-carbon atoms. Accompanying this is an expansion of the routes for synthesis that can be applied generally and more specifically to individual examples to efficiently deliver key building blocks used in drug discovery. This chapter will highlight recent examples of applications of heterocycles to favorably improve drug candidates in a range of therapeutic areas. In addition, synthetic methodology to access these heterocycles, including a discussion of late stage functionalization as a means to create new molecules will be presented.