200 BC

By place

Seleucid Empire

• Antiochus III's forces continue their invasion of Coele Syria and Palestine.
• Conquest of Armenia by the Seleucids.

Greece

• Philip V of Macedon's fleet defeat the Rhodians at Lade. His forces then advance into Pergamum, plundering Pergamese territory and attacking cities in Caria.
• The Acarnanians, with Macedonian support, invade Attica, causing Athens, which has previously maintained its neutrality, to seek help from the enemies of Philip. Attalus I of Pergamum, who is with his fleet at Aegina, receives an embassy from Athens asking him to come to the city for consultations. After he is told that Roman ambassadors are also in Athens, Attalus goes there in haste.
• The Roman ambassador to Greece, Syria, and Egypt, Marcus [Aemilius Lepidus (consul 187 BC)|Marcus Aemilius Lepidus] delivers an ultimatum to Philip V warning Macedonia not to make war on any Greek state. Philip decides to reject the Roman ultimatum and the Romans declare war on Macedon, thus starting the Macedonian War">Macedonia (ancient kingdom)">Macedonian War.
• The Roman consul, Publius [Sulpicius Galba Maximus], asks Attalus I and his fleet to meet up with the Roman fleet off the Greek Aegean coast and they conduct a naval campaign against Philip V, harassing Macedonian possessions in and along the Aegean.

Bactria

• Euthydemus I of the Greco-Bactrian Kingdom dies and is succeeded by his son Demetrius I of Bactria.

South America

• The city of Tiwanaku is founded as a village near Lake Titicaca in modern Bolivia.
• The Early Horizon period in the Andes comes to an end as the Chavin culture vanishes and is succeeded by the Nazca culture.

China

• Chinese create a padding material.
• The construction of the Wei-Yang Palace in the Han dynasty capital begins.
• The Han emperor Gaozu of Han|Gaozu] is defeated by the Xiongnu, led by Modu Chanyu, in the Battle of Baideng.

By topic

Art

• Lost-wax casting is known in China and Mesopotamia.
• Roman artists begin attempting to produce the illusion of thin slabs of colored marble covering the walls, which are set off by actual architectural moldings and columns, in private houses. These attempts last for 120 years.

Astronomy

• The first good measurement of the distance between Earth and the Sun is made by Eratosthenes. By studying lunar eclipses, his result is roughly 150 000 000 km. The currently accepted value is 149 597 870 691 ± 30 metres.