After a brief background on Otto Heinrich Warburg (1883–1970), and some of his selected research, we provide highlights, in English, of three of his papers in the 1940s—unknown to many as they were not originally published in English. They are: two brief reports on Photosynthesis, with Wilhelm Lüttgens, originally published in German, in 1944: ‘Experiment on assimilation of carbonic acid’; and ‘Further experiments on carbon dioxide assimilation’. This is followed by a regular paper, originally published in Russian, in 1946: ‘The photochemical reduction of quinone in green granules’. Since the 1944 reports discussed here are very short, their translations are included in the Appendix, but that of the 1946 paper is provided in the Supplementary Material. In all three reports, Warburg provides the first evidence for and elaborates on light-driven water oxidation coupled to reduction of added benzoquinone. These largely overlooked studies of Warburg are in stark contrast to Warburg’s well-known error in assigning the origin of the photosynthetically formed dioxygen to carbonate.