Philip II of Macedon (Ancient Greek: Φίλιππος, romanized: Phílippos; 382 BC – October 336 BC) was the king (basileus) of the ancient kingdom of Macedonia from 359 BC until his death in 336 BC. He was a member of the Argead dynasty, founders of the ancient kingdom, and the father of Alexander the Great.

The rise of Macedon, including its conquest and political consolidation of most of Classical Greece during his reign, was achieved by his reformation of the army (the establishment of the Macedonian phalanx that proved critical in securing victories on the battlefield), his extensive use of siege engines, and his use of effective diplomacy and marriage alliances.

After defeating the Greek city-states of Athens and Thebes at the Battle of Chaeronea in 338 BC, Philip II led the effort to establish a federation of Greek states known as the League of Corinth, with him as the elected hegemon and commander-in-chief of Greece for a planned invasion of the Achaemenid Empire of Persia. However, his assassination by a royal bodyguard, Pausanias of Orestis, led to the immediate succession of his son Alexander, who would go on to invade the Achaemenid Empire in his father's stead.

Philip was born in either 383 or 382 BC, and was the youngest son of King Amyntas III and Eurydice of Lynkestis. He had two older brothers, Alexander II and Perdiccas III, as well as a sister named Eurynoe. Amyntas later married another woman, Gygaea, with whom he had three sons, Philip's half-brothers Archelaus, Arrhidaeus, and Menelaus.

After the assassination of Alexander II, Philip was sent as a hostage to Illyria by Ptolemy of Aloros. Philip was later held in Thebes (c. 368–365 BC), which at the time was the leading city of Greece. While in Thebes, Philip received a military and diplomatic education from Epaminondas, and lived with Pammenes, who was an enthusiastic advocate of the Sacred Band of Thebes.

In 364 BC, Philip returned to Macedon. In 359 BC, perhaps in May, Philip's other brother, King Perdiccas III, died in battle against the Illyrians. Before leaving, Perdiccas had appointed Philip as regent for his infant son Amyntas IV, but Philip succeeded in taking the kingdom for himself.

Philip's military skills and expansionist vision of Macedonia brought him early success. He first had to remedy the woes over Macedonian territory faced by his throne's government. This was a predicament that had greatly worsened through Macedonia's defeat by the Illyrians, a struggle in which King Perdiccas himself had died. The Paeonians and the Thracians had sacked and invaded the eastern regions of Macedonia, while the Athenians had landed at Methoni on the coast with a contingent under the Macedonian pretender Argaeus II.

Philip pushed back the Paeonians and Thracians promising tributes, and defeated the 3,000 Athenian hoplites (359 BC). Momentarily free from his opponents, he concentrated on strengthening his internal position and, above all, his army. Philip II made many notable contributions to the Macedonian army. The cavalry, which were the primary source of the army's strength, went from a force of 600 to 4000 from the time of the battles with the Illyrians to 334 BC. The discipline and training of the soldiers increased as well, and the Macedonian soldiers under Philip were provided with the possibility of promotion through the ranks and rewards and bonus wages for exceptional service. In addition to these changes, Philip created the Macedonian phalanx, an infantry formation that consisted of soldiers all armed with a sarissa. Philip is credited for adding the sarissa to the Macedonian army, where it soon was the common weapon used by most soldiers.