The oxygen isotope ratio (δ¹⁸O) of tree-ring cellulose provides a valuable climatic record with an annual timescale. In Japan, the cellulose δ¹⁸O records have been accumulated over the past decade. However, no long-term records have been reported for the southern subtropical island, Okinawa-jima, where many long-lived trees were burned during the Second World War and have been periodically damaged by typhoons. Here, we show a cellulose δ¹⁸O of Ryukyu Pine (Pinus luchuensis Mayr.) from the Okinawa-jima island. This δ¹⁸O data, which was obtained from a tree-disk preserved in a University Museum, cover a 95-year period before meteorological observation began on this island in 1891. The cellulose δ¹⁸O variations negatively correlate with the amount of precipitation during the rainy season, suggesting that the cellulose δ¹⁸O values are largely affected by δ¹⁸O of rainwater rather than large scale ENSO variations.