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Abstract: From 1885 to 1967, seawater temperatures have been daily measured at Marseilles. These measurements were used to correct the sea level data of tide-recorder that provided the zero level taken as a reference in France. These data (almost 30 000) are deposited within the National Geographic Institute, where we have manually copied and put them under a digital form. The complete treatment of this well-known but never examined long-time series should provide valuable information inside the context of the global warming and with regards to the lack of historical information on seawater temperature. By comparisons with current Mediterranean surface seawater- and air-temperature series, minima winter averages appear to be too low (about 2°C) for the Mediterranean Sea''s surface, and too high for aerial temperatures. This bias is probably the consequence of the measuring place, which is located inside the float shaft of the tide-recorder, i.e. in an enclosed and not free seawater body. But all the data having been recorded following the same protocol, they can be compared. The statistical treatment of this 83-year series exhibits a significant warming trend, which can be estimated to +0.66°C by a century, and +0.76°C when only the warmest months (June to September) are taken into account. [Copyright &y& Elsevier]