Caesarea Maritima, capital and economic centre of Judaea-Palestine, was a city of many identities – Christian, Greek, Jewish, Roman, Samaritan – and many languages – Aramaic, Greek, Hebrew and Latin. Using the methodology of modern sociolinguistics, I examine how all these different identities and languages interacted. I take a comprehensive approach to our sources for Caesarea, analysing texts in all four of the above languages across the entirety of the Roman period (c. 10 BCE – 640 CE). I focus on the 962 inscriptions from Caesarea, various quotations of Caesarean rabbis in works of rabbinic literature such as the Jerusalem Talmud, and the Greek writings of Eusebius and Procopius, native Caesareans, and Origen, an adopted Caesarean. I argue that Greek served as a unifying language at Caesarea across the different groups, in a way that particularly stands out in the case of the Jews. Latin, meanwhile, has a relatively high presence at first, but eventually disappears, a disappearance which I explain. Finally, Hebrew and Aramaic are less prominent among the Jews of Caesarea than at other parts of the province, but they are still important, especially for the rabbinic movement. Greek-speaking Christian scholars develop a strong interest in Hebrew, but they did not have deep knowledge of the language.