Papyrus 45 (P. Chester Beatty I) is an early Greek New Testament manuscript written on papyrus, and is one of the manuscripts comprising the Chester Beatty Papyri, a group of early Christian manuscripts discovered in the 1930s, and purchased by business man and philanthropist, Alfred Chester Beatty. It is designated by the siglum π in the Gregory-Aland numbering of New Testament manuscripts. Beatty purchased the manuscript in the 1930s from an Egyptian book dealer, and it was subsequently published in The Chester Beatty Biblical Papyri, Descriptions and Texts of Twelve Manuscripts on Papyrus of the Greek Bible by palaeographer, biblical and classical scholar Frederic G. Kenyon in 1933. Manuscripts among the Chester Beatty Papyri have had several places of discovery associated with them, the most likely being the Faiyum in Egypt (the dry sands of Egypt have been a haven for finding very early manuscripts since the late 1800s). Using the study of comparative writing styles (palaeography), it has been dated to the early 3rd century CE. This therefore makes it the earliest example of not only the four Gospels contained in one volume, but also the Acts of the Apostles. It contains verses in fragmentary form from the texts of Matthew chapters 20β21 and 25β26; Mark chapters 4β9 and 11β12; Luke chapters 6β7 and 9β14; John chapters 4β5 and 10β11; and Acts chapters 4β17.
The manuscript is currently housed at the Chester Beatty Library, Dublin, Ireland, except for one leaf containing Matt. 25:41β26:39, which is in the Papyrus Collection of the Austrian National Library in Vienna (Pap. Vindob. G. 31974).