This Special Issue aims to showcase cutting-edge research on numerical modeling and experimental investigation in the characterization of petroleum and its derivatives and bioprocesses. The scope of this Special Issue includes cases of investigations on petroleum property relationships, the modeling of petroleum properties, the application of different methods for the characterization of petroleum and its derivatives, sustainable fuels, biofuels, petroleum refining process performance optimization, and bioprocesses. Included in this Special Issue are seventeen contributions from researchers across the globe in the fields of petroleum fluid characterization and bioprocesses.