From the twelfth century on, the legend of Prester John, a Christian ruler in the far East, spread across Europe. Establishing contacts with the presbyter, the Latins hoped for military as well as economic support regarding their fight against the Muslims and the heathen. Once the power relations in the Arab world had changed and the sultanate of Egypt had become the major opponent of the European Christians, many supporters of the crusades aspired to dry up the Nile and to attack the Muslim empire from two sides. From the 14th century on the Negus of Ethiopia was equated with Prester John more and more. This diploma thesis focusses on the reciprocal contacts between the Christian rulers of Europe and the legendary Presbyter in Africa. To do this, the most significant primary sources are used. In addition, insight into the political endeavors of Ethiopia and the Latin world is provided. With the European expansion of the Portuguese towards Africa, the last great search for Prester John begins. By means of sources it is explained why the mariners set out to Africa to find the presbyter.