|Millennium:||1st millennium BC|
|205 BC by topic|
|Gregorian calendar||205 BC|
|Ab urbe condita||549|
|Ancient Egypt era||XXXIII dynasty, 119|
|- Pharaoh||Ptolemy IV Philopator, 17|
|Ancient Greek era||143rd Olympiad, year 4|
|Balinese saka calendar||N/A|
|Chinese calendar||乙未年 (Wood Goat)|
2492 or 2432
— to —
丙申年 (Fire Monkey)
2493 or 2433
|Coptic calendar||−488 – −487|
|Ethiopian calendar||−212 – −211|
|- Vikram Samvat||−148 – −147|
|- Shaka Samvat||N/A|
|- Kali Yuga||2896–2897|
|Iranian calendar||826 BP – 825 BP|
|Islamic calendar||851 BH – 850 BH|
|Minguo calendar||2116 before ROC|
|Seleucid era||107/108 AG|
|Thai solar calendar||338–339|
−78 or −459 or −1231
— to —
−77 or −458 or −1230
Year 205 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Africanus and Dives (or, less frequently, year 549 Ab urbe condita). The denomination 205 BC 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.
- Returning via the Persian provinces of Arachosia, Drangiana, and Carmania, Antiochus III arrives in Persis. He then leads a short expedition down the Persian Gulf and receives tribute of 500 talents of silver from the citizens of Gerrha, a mercantile state on the east coast of the Persian Gulf.
- Antiochus III returns from his eastern campaigns, after having defeated the Bactrians and subjugated the Parthians and thus being able to partly restore Seleucid power in these provinces by crushing the revolting governors of Media, Persia and Anatolia. Having established a system of vassal states in the East, Antiochus now adopts the ancient Achaemenid title of "great king", and the Greeks, comparing him to Alexander the Great, surname him "the Great", that is to say Antiochus III Megas.
- Philip V of Macedon makes a temporary peace (the Peace of Phoenice) with Rome on favourable terms for Macedonia ending the First Macedonian War. The treaty formally acknowledges the favourable position of Macedonia, including their capture of Illyria, but in return Philip effectively repudiates his alliance with Hannibal.
- After the peace, the Spartan king, Nabis, goes to war with the Achaean League. The Achaean general Philopoemen expels Nabis of Sparta from Messene.
- The Peace of Phoenice prohibits Philip from expanding westward into Illyria or the Adriatic Sea, so the king turns his attentions eastwards to the Aegean Sea, where he starts to build a large fleet. After concluding the First Macedonian War, Philip of Macedon, seeing his chance to defeat Rhodes, forms an alliance with Aetolian and Spartan pirates who begin raiding Rhodian ships. The Cretan War begins between Philips' Macedonians, the Aetolian League, several Cretan cities (of which Olous and Hierapytna are the most important) and Spartan pirates against the forces of Rhodes and later Attalus I of Pergamum, Byzantium, Cyzicus, Athens and Knossos.
- With the Rhodian fleet and economy suffering from the depredations of the pirates, Philip begins attacking the lands of Rhodes' allies in Thrace and around the Sea of Marmara.
- Publius Cornelius Scipio boldly determines to disregard Hannibal in Italy and political opposition in the Roman Senate and rather decides to strike at the Carthaginian holdings in North Africa. Scipio crosses to Sicily with an army consisting partly of volunteers as the Roman Senate would not provide him with an army.
- The Roman propraetor Quintus Pleminius captures the town of Locri Epizephyrii from the Carthaginians. Hannibal's attempt to recapture the town is foiled by the appearance of Scipio's army.
- Scipio sends the Roman general Gaius Laelius to North Africa to prepare the way for his later invasion.
- A Carthaginian army under Mago Barca lands in Liguria, capturing Genoa and Savona.
- Hannibal erects a bilingual Punic/Greek inscription describing his accomplishments in the temple of Juno Lacinia near Crotone.
- The native Egyptian population rises in rebellion against their Greek rulers. The revolt spreads to Upper Egypt.
- Ptolemy IV dies and is succeeded by his five-year-old son Ptolemy V. However, no public announcement is made about the king's death.