Lipid-based drug-delivery nanoparticles, including non-lamellar-type, mesophasic nanostructured materials of lyotropic liquid crystals (LLCs), have been a topic of interest for researchers for their applications in the encapsulation of biopharmaceutical drugs as well as their controlled and targeted release. Cubosomes, derived from LLCs, are self-assembled cubic-phase bicontinuous crystalline nanoparticulate colloidal dispersions. Their lipid bilayers are arranged in 3D space such that they have an uninterrupted, regular cubic symmetrical surface, separated by two interconnected aqueous channels. Thus, they have a large surface area involving numerous internal segments, giving them a definitive advantage over lamellar liposomes in facilitating the efficient entrapment and sustained release of active therapeutic substances. This Review focuses on the unique properties of cubosomes, such as their ability to encapsulate hydrophobic, hydrophilic, and amphiphilic bioactive substances, which make them attractive for the encapsulation and release of therapeutic molecules, including large biomolecules. Controlled drug release via functionalization has demonstrated cubosomes as a potential vehicle for various administration routes. Their self-assembling properties make their production uncomplicated, with two major manufacturing methods: the top-down and bottom-up methods. Cubosomes are formed when amphiphilic lipids, such as monoolein, monolinolein, phytantriol, etc., self-assemble into non-lamellar bicontinuous cubic phases in excess water. In this Review, we have endeavored to outline the composition, preparation techniques, drug-encapsulation approaches, and drug-loading and -release mechanisms of cubosomes. Furthermore, the prospective routes for cubosomes, their challenges, and future potentialities are addressed.