The fused nitrogen-rich heterocycles, particularly planar structures, possess many advantages over conventional single-ring energetic compounds. The planar pi-pi stacked structures result in enhanced safety. Meanwhile, their conjugated systems give rise to good energetic properties. This review focused on the syntheses, properties, and potential applications of energetic materials based on the coplanar fused nitrogen-rich heterocycles. Most of these compounds exhibit excellent detonation characteristics along with low mechanical sensitivity which makes them very promising candidates for highly energetic materials for civilian or military applications.