The 4th century BC started the first day of 400 BC and ended the last day of 301 BC. It is considered part of the Classical era, epoch, or historical period.
This century marked the height of Classical Greek civilization in all of its aspects. By the year 400 Greek philosophy, art, literature and architecture had spread far and wide, with the numerous independent Greek colonies that had sprung up throughout the lands of the eastern Mediterranean.
Arguably the most important series of political events in this period were the conquests of Alexander, bringing about the collapse of the once formidable Persian Empire and spreading Greek culture far into the east. Alexander dreamed of an east/west union, but when his short life ended, his vast empire was plunged into civil war as his generals each carved out their own separate kingdoms. Thus began the Hellenistic age, a period characterized by a more absolute approach to rule, with Greek kings taking on royal trappings and setting up hereditary successions. While a degree of democracy still existed in some of the remaining independent Greek cities, many scholars see this age as marking the end of classical Greece.
In India, the Mauryan Empire was founded in 322 BC by Chandragupta Maurya, who had overthrown the Nanda Dynasty and rapidly expanded his power westwards across central and western India, taking advantage of the disruptions of local powers in the wake of the withdrawal westward by the armies of Alexander.
China in the 4th century BC entered an era of constant warfare known as the Warring States period. The period saw the rapid rise of large states (such as Chu) over smaller ones thanks to technological advancement. Though the period has usually been characterized by historians as being excessively violent compared to the Spring and Autumn period it was also punctured by several cultural and social growth through the expansion of several different sects of Confucianism and Taoism.
Oldest Brāhmī script dates from this period. Brāhmī is the ancestor of Brahmic scripts, used in much of India and Southeast Asia.
Romans build their first aqueduct.
Chinese use the handheld trigger crossbow for the first time.
The first crossbow, the gastraphetes, is invented at Syracuse. (? pre-421 BC)
Burnt brick first used in Greece.
Donkey-powered mills first used in Greece.
In Greece, Aristotle proposes the division of the known sciences.
Torque with lion's-head terminals, from Susa (modern Shush, Iran) was made. It is now in Musée du Louvre, Paris.
Daric, a coin first minted under Darius I of Persia is made. It is now kept in Heberden Coin Room, Ashmolean Museum, Oxford.
Second half of the 4th century BC – Tomb II, so called Tomb of Philip II of Macedon, Vergina, Macedonia is made.
Starting in the year 309 BC, the later Chinese historian Sima Qian (145 BC–90 BC) wrote that the Qin-employed engineer Bi Ling of the newly conquered State of Shu in Sichuan had the shoulder of a mountain cut through, making the 'Separated Hill' that abated the Mo River, and excavated two canals in the plain of Chengdu. The significance of this was phenomenal, as it allowed the new Guanxian irrigation system to populate an area of some 40 by 50 miles (60 × 80 km) with over five million people, still in use today (Needham, Science and Civilization in China, Volume 4, Part 3, 288).
The Chinese astronomer Gan De divides the celestial sphere into 365¼ degrees, and the tropical year into 365¼ days at a time when most astronomers used the Babylon division of the celestial sphere as 360 degrees (Deng, Yinke.  (2005). Chinese Ancient Inventions. ISBN 7-5085-0837-8).
Agnodice, female Athenian physician and midwife
Alexander the Great, king of Macedon
Antigonus I Monophthalmus, Macedonian diadoch
Antipater, Macedonian statesman
Atropates, Persian nobleman
Bessus, Persian satrap of Bactria
Cassander, King of Macedon
Chandragupta Maurya, Founder of the "Mauryan Dynasty"
Craterus, Macedonian diadoch
Darius III, king of the Achaemenid Empire
Demetrius Poliocretes, King of Macedon
Demosthenes, Athenian statesman and orator
Dhana Nanda, last emperor of the Nanda dynasty
Duke Xiao of Qin, ruler of Qin
Epaminondas, Theban statesman
Hephaestion, Macedonian general
King Wuling of Zhao, ruler of Zhao
Lysimachus, Macedonian diadoh and king of Thrace
Mahapadma Nanda, founding emperor of the Nanda dynasty
Manius Curius Dentatus, Roman statesman
Nakhthorheb, last native Pharaoh of Egypt
Pang Juan, Chinese general
Parmenion, Macedonian general
Pelopidas, Theban statesman
Perdiccas, Macedonian diadoh
Philip II, King of Macedon
Ptolemy I Soter, Macedonian diadoh and king of Egypt
Seleucus I Nicator, Macedonian diadoh and founder of the Seleucid Empire
Shang Yang, Chinese statesman
Su Qin, Chinese politician and strategist
Tian Ji, Chinese general
Zhang Yi, Chinese strategist
Apelles, Greek painter
Cephisodotus the Elder, Greek sculptor
Leochares, Greek sculptor
Lysippos, Greek sculptor
Praxiteles, Greek sculptor
Scopas, Greek sculptor and architect
Menander, Greek playwright
Onesicritus, Greek historical writer
Qu Yuan, Chinese poet
Simonides of Ceos, Greek lyric poet
Xenophon, Greek historian and writer
Anaximenes of Lampsacus, Greek rhetorician and historian.
Antisthenes, Greek philosopher
Archytas, Greek philosopher
Aristippus, Greek philosopher
Aristotle, Greek philosopher
Callisthenes, Greek historian
Chanakya, Indian economist and political advisor
Crates of Thebes, Greek philosopher
Demetrius of Phalerum, Greek orator
Diogenes of Sinope, Greek philosopher
Epicurus, Greek philosopher
Mencius, Chinese philosopher
Panini, Indian philosopher and writer
Plato, Greek philosopher
Pyrrho, Greek philosopher
Speusippus, Greek philosopher
Sun Bin, Chinese author & military strategist
Theophrastus, Greek philosopher
Wu Qi, Chinese military strategist & philosopher
Xenocrates, Greek philosopher
Zeno of Citium, Greek philosopher
Zhuangzi, Chinese philosopher
4th century BC Wikipedia
See: List of sovereign states in the 4th century BC.