Estimating the accurate estimating the reference crop evapotranspiration is crucial in irrigation planning and determining irrigation intervals. The aim of this study was to compare and evaluate fourteen different methods for estimating reference crop evapotranspiration in three general categories: temperature-based (Hargreaves-Samani, Blaney-Criddle, Linacre, and Schendel), radiation-based (Priestley-Taylor, McKing, Turc, Jensen-Haise, and Irmak), and mass transfer-based (Meyer, Dalton, Trabert, WMO, and Albrecht) in eight study stations in Khuzestan province from 2007 to 2023. The results of these methods were compared with the results obtained from the FAO Penman-Monteith method. The performance evaluation of different methods was performed using R2, RMSE, and MBE statistics. The results showed that in most of the study stations, among the temperature-based methods, the Linacre method with R2 between 0.747 and 0.954 had the best performance, and the Hargreaves method with R2 between 0.7 and 0.91 had the worst performance. Among the solar radiation-based methods, the Jensen-Haise method with R2 between 0.723 and 0.936 had the best performance, and the Priestley-Taylor method with R2 between 0.27 and 0.75 had the worst performance. Among the mass transfer-based methods, the Albrecht method with R2 between 0.6 and 0.968 in 75% of the stations (six stations), the Dalton method with R2 of 0.982 in Izeh station, and the WMO method with R2 of 0.967 in Shushtar station had the best performance. The Meyer method had weaker performance in all stations with R2 between 0.6 and 0.9. Researchers are advised that if sufficient information is not available to calculate evapotranspiration using the FAO Penman-Monteith (PMF-56) reference method, they should use the aforementioned methods that had the best results in the study stations in Khuzestan province.