This symposium will cover recent advances and emerging opportunities in the design, synthesis and characterization of bulk (powders), thin films, and single crystal materials hosting multiple anions. Heteroanionic materials are novel compounds where the anion sublattice involves two or more anionic species and are distinct from polyanionic compounds with oxyanions. They have generated growing interest within the materials science, solid state chemistry, and physics communities arising from the tremendous possibilities they offer to tune chemical bonding through multiple anions, leading to diverse functional properties.In addition, the symposium will highlight worldwide efforts focused on material families such as oxyhydrides, oxyhalides, oxynitrides, and oxychalcogenides that exhibit enhanced or novel function in areas such as catalysis, optical responses, electronic and resistive switching behavior, electrochemical energy storage, ionic conductivity, magnetism, ferroelectricity, and spin-orbit-based phenomena. Computational approaches will be presented that deliver materials design guidelines to accelerate new multiple anion materials discovery as well as provide insight into relationships between anionic bonding environments and electronic band structure. Talks will feature advances in synthesis activities to realize new heteroanionic materials, including energy efficient approaches or those that can be applied to epitaxial heterostructures in thin films. The application of advanced imaging, scattering, and spectroscopic characterization techniques to elucidate structure-property relationships, as well as performance in energy and electronic applications will be covered in the symposium. Speakers will also identify emerging opportunities and future directions, for instance in heteroanionic topological/quantum materials, in situ characterization of topochemical or other synthetic approaches, and data-centered materials discovery.