|Centuries:||3rd century – 4th century – 5th century|
|Decades:||290s 300s 310s – 320s – 330s 340s 350s|
|Years:||321 322 323 – 324 – 325 326 327|
|324 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||1077|
|Bahá'í calendar||−1520 – −1519|
|English Regnal year||N/A|
|Chinese calendar||癸未年 (Water Goat)
3020 or 2960
— to —
甲申年 (Wood Monkey)
3021 or 2961
|- Vikram Samvat||380–381|
|- Shaka Samvat||246–247|
|- Kali Yuga||3425–3426|
|Igbo calendar||−676 – −675|
|Iranian calendar||298 BP – 297 BP|
|Islamic calendar||307 BH – 306 BH|
|Minguo calendar||1588 before ROC
|Thai solar calendar||867|
|Wikimedia Commons has media related to 324.|
Year 324 (CCCXXIV) was a leap year starting on Wednesday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Crispus and Constantinus (or, less frequently, year 1077 Ab urbe condita). The denomination 324 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
- July 3 – Battle of Adrianople: Emperor Constantine the Great defeats his rival Licinius near Adrianople, forcing him to retreat to Byzantium. He invades Thrace with a Visgothic force and raids the countryside. This sees Constantine ruling as sole Emperor.
- July – Battle of Hellespont: Crispus, destroys Licinius' naval fleet in the Dardanelles, allowing his father Constantine the ability to cross over the Bosporus into Asian provinces. Byzantium is besieged and Licinius assembled a second military force, under his newly elevated co-emperor Martinian at Lampsacus (modern Lapseki).
- September 18 – Battle of Chrysopolis: Constantine I definitively defeats Licinius at Chrysopolis, and becomes sole Emperor, thus ending the period of the Tetrarchy. Licinius escapes and gathered around 30,000 of his surviving troops at Nicomedia.
- December 19 – Licinius abdicates his position as Emperor. He is pardoned by Constantine I as a result of the supplication of his wife Constantia (who is Constantine's halfsister), and banished to Thessalonica as a private citizen.
- December 20 – Philogonus, Patriarch of Antioch
- Guo Pu, Chinese writer (b. 276)
- Wang Dun, general of the Jin Dynasty (b. 266)
- Zhang Mao, ruler of Former Liang (b. 277)