For my thesis, I propose the topic "The Philadelphia Diocese and the Metropolitan of Philadelphia, His Eminence Bartholomew Arhondonis." In order to write this thesis, I researched documents and compiled a bibliography from the Library of the Ecumenical Patriarch at the School of Theology in Halki. Moreover, this thesis, which is a graduate thesis, has three chapters (parts). The first part includes a short biography of Bartholomew, Archbishop of Constantinople, New Rome, and the Ecumenical Patriarch. The second part mentions the historical evolution of the Holy Diocese of Philadelphia (which Metropolitans preceded him, where it is located geographically, and its composition, etc.). The third and foremost part of this thesis refers to Bartholomew, Archbishop of Constantinople, New Rome, and Ecumenical Patriarch as the Philadelphia Metropolitan and the role he played in its administration. I plan to talk about his achievements, which led to his success in being elected the Patriarch of Constantinople. In particular, I will present some of the addresses delivered by the Metropolitan of Philadelphia, His Eminence Bartholomew. I will write about some special events that the Metropolitan of Philadelphia attended. We observe that the Metropolitan of Philadelphia was very close to the Ecumenical Patriarch, and we can add that he was one of the most important collaborators of the Ecumenical Patriarch.