Editing 4th century BC (section)

===[[300s BC (decade)|300s BCE]]===
* [[309 BCE]]: [[Ptolemy I Soter|Ptolemy]] personally commands a fleet that captures the coastal regions of [[Lycia]] and [[Caria]] from Antigonus.
* [[309 BCE]]: [[Cassander]], who has held [[Roxana]], widow of [[Alexander the Great]], in prison for a number of years, has her put to death along with her young son Alexander, the nominal King [[Alexander IV of Macedon]].
* [[309 BCE]]: Soon after the [[Qin (state)|State of Qin]] has conquered the [[Shu (state)|State of Shu]] (in modern-day [[Sichuan]] province), they employ the Shu engineer Bi Ling to create the Guanxian [[irrigation]] system, which will eventually provide for over five million people in an area of 40 to {{convert|50|sqmi|km2}}, still in use today.
* [[308 BCE]]: [[Ptolemy I Soter|Ptolemy]] crosses from [[Asia Minor]] into [[Ancient Greece|Greece]], where he takes possession of [[Corinth]], [[Sicyon]] and [[Megara]].<ref name="Diodorus37">{{cite book|last=Siculus|first=Diodorus|title=Library|url=https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Diodorus_Siculus/20B*.html#37|volume=XX|chapter=37}}</ref>
* [[308 BCE]]: [[Ptolemy I Soter|Ptolemy]] makes peace with [[Cassander]]<ref name="Diodorus37" />
* [[308 BCE]]: [[Cleopatra of Macedon]] is assassinated by the order of [[Antigonus I Monophthalmus|Antigonus]]<ref name="Diodorus37" />
* [[307 BCE]]: [[Ptolemy I Soter|Ptolemy]] founds the [[Musaeum|Museum]] and [[Library of Alexandria]] with the help of Demetrius Phalereus. Like [[Alexander the Great]], Ptolemy has studied under [[Aristotle]] and staffs the museum with some 100 professors paid by the state.
* [[307 BCE]]: The city of [[Segesta]] in Sicily is destroyed by Agathocles.
* [[307 BCE]]: The Chinese [[King Wuling of Zhao]] reforms the military of the [[Zhao (state)|State of Zhao]] by putting more emphasis on [[cavalry]] over [[chariot]]eers.
* [[304 BCE]]: The tyrant [[Agathocles]] takes on the title of King of [[Sicily]]. He extends his influence into southern [[Italy]] and the [[Adriatic]].
* [[304 BCE]]: The [[Maurya]]n emperor [[Chandragupta Maurya|Chandragupta]] defeats [[Seleucus I Nicator|Seleucos I]] as he tries to invade [[India]]. [[Seleucid Empire]]'s Eastern [[Satrap|Satrapies]] ceded to [[Maurya Empire|Mauryan]] Empire.
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* [[301 BCE]]: The southern part of Syria is occupied by [[Ptolemy I Soter|Ptolemy]].
* [[300 BC|300 BCE]]: The end of the [[4th century BC]], and the start of the [[3rd century BC]].