There is no single "father of oxygen" in the sense of a person who created oxygen. Oxygen exists naturally. However, depending on the context, several individuals can be considered pivotal figures in our understanding and use of oxygen:
The Discovery of Oxygen: Joseph Priestley
Joseph Priestley is widely credited with the discovery of oxygen in 1774. His work answered long-standing questions about combustion and how things burn. This is supported by the ACS website. While he didn't create oxygen, his experiments significantly advanced scientific knowledge.
The Father of Oxygen Therapy: John Scott Haldane
John Scott Haldane is considered the "Father of Oxygen Therapy." His research was crucial in understanding oxygen's role in physiology and its therapeutic applications. Multiple sources (PubMed, PMC) refer to him with this title due to his significant contributions to the field.
The Father of Modern Chemistry: Antoine-Laurent Lavoisier
Antoine-Laurent Lavoisier is considered the "father of modern chemistry." His work was pivotal in understanding oxygen's role in chemical reactions and he was the first to correctly name and explain it as a chemical element. This is corroborated by the Science History Institute.
Therefore, the answer depends on the specific aspect of oxygen you are focusing on: discovery, therapeutic use, or its role in chemistry.