Philip the Arab (Latin: Marcus Julius Philippus "Arabs"; c. 204 – September 249) was Roman emperor from 244 to 249. He was born in Aurantis, Arabia, in a city situated in modern-day Syria.

Philip's rise to prominence began through the intervention of his brother Priscus, who was an important official under the emperor Gordian III.  His big break came in 243, during Gordian III's campaign against Shapur I of Persia, when the Praetorian prefect Timesitheus died under unclear circumstances.  At the suggestion of his brother Priscus, Philip became the new Praetorian prefect, with the intention that the two brothers would control the young Emperor and rule the Roman world as unofficial regents.  Following a military defeat, Gordian III died in February 244 under circumstances that are still debated. While some claim that Philip conspired in his murder, other accounts (including one coming from the Persian point of view) state that Gordian died in battle. Whatever the case, Philip assumed the purple robe following Gordian's death.

Philip was not willing to repeat the mistakes of previous claimants, and was aware that he had to return to Rome in order to secure his position with the Senate. However, his first priority was to conclude a peace treaty with Shapur, and withdraw the army from a potentially disastrous situation.  Although Philip was accused of abandoning territory, the actual terms of the peace were not as humiliating as they could have been.  Philip apparently retained Timesitheus’ reconquest of Osroene and Mesopotamia, but he had to agree that Armenia lay within Persia's sphere of influence.  He also had to pay an enormous indemnity to the Persians of 500,000 denarii. Philip immediately issued coins proclaiming that he had made peace with the Persians (pax fundata cum Persis). 

Leading his army back up the Euphrates, south of Circesium Philip erected a cenotaph in honor of Gordian III, but his ashes were sent ahead to Rome, where he arranged for Gordian III's deification.  Whilst in Antioch, he left his brother Priscus as extraordinary ruler of the Eastern provinces, with the title of rector Orientis. Moving westward, he gave his brother-in-law Severianus control of the provinces of Moesia and Macedonia. He arrived in Rome in the late summer of 244, where he was confirmed augustus.  Before the end of the year, he nominated his young son caesar (heir), his wife, Marcia Otacilia Severa, was named augusta, and he also deified his father Marinus, even though the latter had never been emperor. While in Rome, Philip also claimed a victory over the Persians with the titles of Persicus Maximus, Parthicus Maximus and Parthicus Adiabenicus (the latter probably unofficially.)

In an attempt to shore up his regime, Philip put a great deal of effort in maintaining good relations with the Senate, and from the beginning of his reign, he reaffirmed the old Roman virtues and traditions.  He quickly ordered an enormous building program in his home town, renaming it Philippopolis, and raising it to civic status, while he populated it with statues of himself and his family.  He also introduced the Actia-Dusaria Games in Bostra, capital of Arabia. This festival combined the worship of Dushara, the main Nabataean deity, with commemoration of the Battle of Actium, as part of the Roman Imperial cult.

The creation of the new city of Philippopolis, piled on top of the massive tribute owed to the Persians, as well as the necessary donativum to the army to secure its acceptance of his accession, made Philip desperately short of money. To pay for it, he ruthlessly increased levels of taxation, while at the same time he ceased paying subsidies to the tribes north of the Danube that were vital for keeping the peace on the frontiers.  Both decisions would have significant impacts upon the empire and his reign.

In 245, Philip was forced to leave Rome as the stability established by Timesitheus was undone by a combination of his death, Gordian's defeat in the east and Philip's decision to cease paying the subsidies.  The Carpi moved through Dacia, crossed the Danube and emerged in Moesia where they threatened the Balkans.  Establishing his headquarters in Philippopolis in Thrace, he pushed the Carpi across the Danube and chased them back into Dacia, so that by the summer of 246, he claimed victory against them, along with the title "Carpicus Maximus".  In the meantime, the Arsacids of Armenia refused to acknowledge the authority of the Persian king Shapur I, and war with Persia flared up again by 24

Nevertheless, Philip was back in Rome by August 247, where he poured more money into the most momentous event of his reign – the Ludi Saeculares, which coincided with the one thousandth anniversary of the foundation of Rome.  So in April 248 AD (April 1001 A.U.C.), Philip had the honor of leading the celebrations of the one thousandth birthday of Rome, which according to the empire's official Varronian chronology was founded on 21 April 753 BC by Romulus.

Commemorative coins were issued in large numbers and, according to contemporary accounts, the festivities were magnificent and included spectacular games, ludi saeculares, and theatrical presentations throughout the city.  In the Colosseum, in what had been originally prepared for Gordian III's planned Roman triumph over the Persians,  more than 1,000 gladiators were killed along with hundreds of exotic animals including hippos, leopards, lions, giraffes, and one rhinoceros. The events were also celebrated in literature, with several publications, including Asinius Quadratus' History of a Thousand Years, specially prepared for the anniversary. At the same time, Philip elevated his son to the rank of co-augustus.

Despite the festive atmosphere, there were continued problems in the provinces.  In late 248, the legions of Pannonia and Moesia, dissatisfied with the result of the war against the Carpi, rebelled and proclaimed Tiberius Claudius Pacatianus emperor. The resulting confusion tempted the Quadi and other Germanic tribes to cross the frontier and raid Pannonia. At the same time, the Goths invaded Moesia and Thrace across the Danube frontier, and laid siege to Marcianopolis, as the Carpi, encouraged by the Gothic incursions, renewed their assaults in Dacia and Moesia. Meanwhile, in the East, Marcus Jotapianus led another uprising in response to the oppressive rule of Priscus and the excessive taxation of the Eastern provinces.  Two other usurpers, Marcus Silbannacus and Sponsianus, are reported to have started rebellions without much success.

Overwhelmed by the number of invasions and usurpers, Philip offered to resign, but the Senate decided to throw its support behind the emperor, with a certain Gaius Messius Quintus Decius most vocal of all the senators.  Philip was so impressed by his support that he dispatched Decius to the region with a special command encompassing all of the Pannonian and Moesian provinces. This had a dual purpose of both quelling the rebellion of Pacatianus as well as dealing with the barbarian incursions.

Although Decius managed to quell the revolt, discontent in the legions was growing. Decius was proclaimed emperor by the Danubian armies in the spring of 249 and immediately marched on Rome.  Yet even before he had left the region, the situation for Philip had turned even more sour. Financial difficulties had forced him to debase the antoninianus, as rioting began to occur in Egypt, causing disruptions to Rome's wheat supply and further eroding Philip's support in the capital.

Although Decius tried to come to terms with Philip,  Philip's army met the usurper near modern Verona that summer. Decius easily won the battle and Philip was killed sometime in September 249,  either in the fighting or assassinated by his own soldiers who were eager to please the new ruler.  Philip's eleven-year-old son and heir may have been killed with his father and Priscus disappeared without a trace.

Philip was betrayed and killed at the Battle of Verona in September 249 following a rebellion led by his successor, Gaius Messius Quintus Decius. Philip's reign of five years was uncommonly stable in a turbulent third century.