Calcium oxide catalyst derived from eggshell waste was used for biodiesel production via transesterification of sunflower oil. The eggshell waste was calcined in air at 900 °C for 4 hours to convert the calcium carbonate present in the eggshells into active calcium oxide catalyst. To identify the composition of the CaO catalyst obtaiCalcium oxide catalyst derived from eggshell waste was used for biodiesel production via transesterification of sunflower oil. The eggshell waste was calcined in air at 900 °C for 4 hours to convert the calcium carbonate present in the eggshells into active calcium oxide catalyst. To identify the composition of the CaO catalyst obtained from eggshell waste, X ray fluorescence (XRF) was used. The fatty acid composition of the sunflower oil was also determined by gas chromatography (GC). A factorial design of experiments was employed to evaluate the effect of various parameters (reaction time, methanol to oil molar ratio, and catalyst amount). The use of CaO catalyst derived from eggshell waste for biodiesel production gave a high yield of >95 wt.%. The catalyst performance was achieved at 60 °C, with a reaction time of 4 hours and a methanol to oil molar ratio of 12. Producing CaO catalyst simply by calcining eggshell waste provides an opportunity to use this waste material as an effective catalyst for biodiesel production from sunflower oil. The biodiesel yield remained above 75 wt.% after five cycles of recovery and reuse, which are promising results for the industrial application of this catalyst.