Hellenica Oxyrhynchia is the name given to a history of the late 5th and early 4th centuries BC in ancient Greece, of which papyrus fragments were unearthed at Oxyrhynchus, in Egypt. One of the two major fragments, called the London papyrus, found in 1906, deals with battles in the late Peloponnesian War, particularly the Battle of Notium. The other, the Florentine papyrus, found in 1934, deals with events in the early 4th century. The entire history seems to have been a continuation of Thucydides covering events from 411 BC to 394 BC, much like Xenophon's Hellenica.
The discovery of the first papyrus in 1906 led to a shift in the degree of credence which historians assigned to the ancient sources of the period. In the 19th century, Xenophon, a contemporary of the events he described, was presumed to be universally preferable to the much later Diodorus Siculus. The Oxyrhynchus historian (named "P." for "papyrus"), however, whose work won praise for its pragmatism and style, was found to agree more with Diodorus's account than with Xenophon's on several key issues. This led to a re-evaluation of the values of these sources, and modern historians now prefer Diodorus' account at a number of points.
Modern scholars have debated extensively over P's identity. Among the historians suggested at early stages have been such prominent names as Ephorus and Theopompus, but most of these have been strongly objected to on grounds of style, presentation, or subject matter. At present the most likely candidate seems to be Cratippus, an Athenian historian of the 4th century. The style, biases, and coverage (Cratippus's work is known to have been a continuation of Thucydides) support the identification, although issues have been raised. Bruno Bleckmann, an expert on ancient historiography, has pleaded again for Theopompus as the author of the Hellenica.
Whoever he was, the historian P "is a competent and most conscientious historian who derives his material from the best possible sources, makes an effort to interpret it impartially, but somehow lacks distinction in thought and style. He is a second-rate Thucydides," H.D. Westlake observed.