Year 336 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Crassus and Duillius (or, less frequently, year 418 Ab urbe condita). The denomination 336 BC for this year has been used since the early medieval period, when the Anno Dominicalendar era became the prevalent method in Europe for naming years.
The young king of Persia, Arses, objects to being controlled by Bagoas and attempts to poison him. Instead, Arses and all his children are killed by Bagoas.
Bagoas then seeks to install a new monarch who will be easier to control. He chooses Codomannus, a distant relative of the royal house, who takes the name Darius III. When Darius tries to assert his independence from Bagoas' control, Bagoas attempts to poison him, but the king is warned and forces Bagoas to drink the poison himself.
Macedonian troops, commanded by Parmenion, trusted lieutenant of Philip II, arrive in Asia Minor, but are driven back by Persian forces under the command of the Greek mercenary Memnon of Rhodes.
At a grand celebration of his daughter Cleopatra's marriage to Alexander I of Epirus (brother of Olympias), Philip II is assassinated at Aegae by Pausanias of Orestis, a young Macedonian noble with a bitter grievance against the young queen's uncle Attalus and against Philip for denying him justice. Pausanias is killed on the spot.
Philip II of Macedon is succeeded by his son Alexander III. One of the leading generals in Macedonia at the death of Philip II, Antipater, helps to secure the succession to the Macedonian throne for Alexander.
The Macedonian general Parmenion declares for Alexander III and assists in the murdering of the princes of the Lynkestis region, who are alleged to be behind Philip's murder, along with other possible rivals and members of factions opposed to Alexander. Olympias, Alexander's mother, has Philip's last wife Eurydice, her infant daughter and her influential uncle, Attalus, killed.
Alexander puts down a rebellion in Macedonia and crushes the rebellious Illyrians. He then appears at the gates of Thebes and receives the city's submission. After that he advances to the Corinthian isthmus and is elected by the assembled Greeks as their commander against Persia.
Conscription is introduced in Athens. Young men are required to perform duties which are part military and part civic.