Summary: The main goal of this Special Issue was to contribute to, highlight and discuss topics related to various aspects of two-phase gas-liquid flows, which can be used both in fundamental sciences and practical applications, and we believe that this main goal was successfully achieved. This Special Issue received studies from Russia, China, Thailand, ROC-Taiwan, Saudi Arabia, and Pakistan. We were very grateful to see that all the papers presented findings characterized as unconventional, innovative, and methodologically new. We hope that the readers of the journal Water can enjoy and learn about the experimental and numerical study of two-phase flows from the published material, and share these results with the scientific community, policymakers and stakeholders. Last but not least, we would like to thank Ms. Aroa Wang, Assistant Editor at MDPI, for her dedication and willingness to publish this Special Issue. She is a major supporter of the Special Issues, and we are indebted to her.