Chronic respiratory diseases are the third most frequent cause of death worldwide. However, the limited availability of transplantable organs led to an increased research effort in artificial lung systems. Current artificial lung systems use hollow fibre membrane-based oxygenators. Historic oxygenators using a direct liquid-gas or liquid-liquid interface outperformed todays hollow-fibre technology in terms of gas-transfer. However, these approaches were no longer pursued due to risk of embolization by gas or liquid droplet formation in the blood stream. The herein presented approach of a membrane-supported liquid-liquid oxygenator combines todays hollow-fibre technology with historic liquid-liquid approaches to achieve a stable interface without the risk of embolization but with the advantages of a higher gas-transfer and a decreasing foreign membrane surface of the oxygenator. Perfluoro-n-hexane was chosen as a hemocompatible carrier fluid for the presented liquid-liquid approach. In the proof-of-principle oxygenator, O2 and CO2 gas-transfers were measured to be 1.83 mmolO2 and 1.34 mmolCO2, respectively. No Perfluoro-n-hexane droplets were detected in the blood after the experiment. This study demonstrates the proof of principle of a new membrane-supported liquid-liquid oxygenator.