In recent years, bionanofluids have attracted much attention. These fluids are produced by dispersing bioderived nanoparticles (NPs) in a base fluid. The resulting bionanofluids are reported to show enhanced thermal, electrical, and rheological characteristics with the potential to play crucial roles in industrial applications. This chapter includes an introduction, characterizations, properties, and applications of bionanofluids. The thermo physical, electrokinetic, and rheological properties of bionanofluids have been addressed in subsequent sections. Moreover, potential applications of bionanofluids for heat transfer, mass transfer, biomedicine, and energy will be also discussed in this chapter. Finally, we outline the challenges and future work in the bionanofluids and point out the urgent need for the comprehensive studies to understand properties, characteristics, and applications of the bionanofluids.