This chapter reviews recent advances in chemical synthesis, selfassembly, and applications of novel magnetic nanomaterials in the past few years. The chemical syntheses of several important classes of magnetic nanoparticles are covered, including ferrites, metallic iron, cobalt, alloys, and rare-earth hard magnets. Several examples of shapecontrolled synthesis of nanoparticles and shape-induced texture in selfassembled nanoparticle superlattices are also outlined. Potential applications, particularly in data storage, permanent magnet and biomedicine, of these nanoparticles and assemblies are discussed.