The century immediately before the 1st century AD is called the 1st century BC (or 1st century BCE). It spans the years 100 BC to 1 BC, and there is no “year zero” between them. The year 1 BC jumps straight to AD 1. This period was one of the most transformative in human history: the Roman Republic collapsed into an empire, Han China reached its peak, Cleopatra’s Egypt fell, and roughly 261 million people lived on Earth.
Why There Is No Year Zero
The calendar system most of the world uses today was designed in 525 AD by a monk named Dionysius Exiguus, who created it to calculate the date of Easter. He labeled years as either AD (Anno Domini, “Year of our Lord”) or BC (“Before Christ”), starting his count at year 1. The concept of zero didn’t exist in Roman numerals, so no year zero was ever included. That means counting backward from AD 1 lands you directly in 1 BC. Between January 1 of 500 BC and January 1 of AD 500, only 999 years pass, not 1,000.
Today, many scholars and scientists use BCE (“Before Common Era”) and CE (“Common Era”) instead of BC and AD. The dates are identical. 44 BC is the same year as 44 BCE. The labels simply remove the religious reference, making the system more universal.
The 1st Century BC at a Glance
The 1st century BC (100 BC to 1 BC) sits at the tail end of the Iron Age in archaeological terms, though by this point historians typically describe periods by the civilizations that dominated them: Persian, Hellenistic, Roman. The Iron Age had formally ended centuries earlier in the Near East, around 586 BC, when the Babylonian Empire destroyed the last independent states of the Levant. By the 1st century BC, the world’s power was concentrated in a handful of massive empires spanning Europe, Asia, and North Africa.
Rome: From Republic to Empire
The single biggest political transformation of the 1st century BC was the death of the Roman Republic and the birth of the Roman Empire. At the start of the century, Rome was already the dominant power in the Mediterranean, but it governed itself through elected officials and a senate. That system was fracturing under the weight of civil wars, military strongmen, and class conflict.
In 82 BC, the general Lucius Cornelius Sulla seized power as dictator. He resigned in 79 BC, but the precedent was set: a single man could take control of the state by force. By 60 BC, Julius Caesar had risen to prominence. He conquered Celtic Gaul (modern France) by 51 BC, pushing Rome’s borders beyond the Mediterranean for the first time. Caesar was assassinated in 44 BC by senators who feared he was destroying the Republic.
What followed was another round of civil war. Caesar’s adopted heir, Octavian, fought alongside and then against Mark Antony for control of Rome. In 31 BC, Octavian defeated Antony at the Battle of Actium and became the sole ruler. In 27 BC, the Roman Senate granted him the title Augustus, making him the first Roman emperor. Augustus held power until his death in AD 14, and his reign launched an era of relative stability known as the Pax Romana. The Roman Republic, which had lasted nearly 500 years, was gone.
Han China and the Parthian Empire
Rome wasn’t the only superpower. On the other side of the world, China’s Western Han dynasty controlled a vast territory stretching from the Pacific coast deep into Central Asia. Emperor Wu, who ruled from 141 to 87 BC, expanded the empire aggressively and opened the Silk Road trade routes connecting China to Persia and eventually Rome. After Wu’s death, the dynasty continued through a series of emperors, though internal instability grew toward the end of the century. Emperor Ping, who took the throne in 1 BC, would be the last Western Han ruler before a brief usurpation temporarily ended the dynasty.
Between Rome and China sat the Parthian Empire, covering modern-day Iran, Iraq, and parts of Central Asia. The Parthians were a major military and commercial power. Under Mithridates II (who ruled from 124 to 88 BC), the empire reached its greatest extent and began direct diplomatic contact with both Rome and China. For much of the 1st century BC, the Parthians served as the crucial middle link in transcontinental trade, profiting enormously from goods moving along the Silk Road.
The Fall of Ptolemaic Egypt
Egypt in the 1st century BC was ruled by the Ptolemaic dynasty, descendants of one of Alexander the Great’s generals. Ptolemaic Egypt was the wealthiest of the kingdoms that had emerged after Alexander’s death, and the last to fall under direct Roman control. Its final ruler was Cleopatra VII, who took the throne in 51 BC at age 17.
Cleopatra allied herself with Julius Caesar and later with Mark Antony, using those relationships to preserve Egyptian independence. After Octavian defeated Antony in 31 BC, both Antony and Cleopatra fled to Egypt. Antony died after his final battle, and Cleopatra committed suicide on August 12, 30 BC. She was 39 and had been queen for 22 years. With her death, Egypt became a Roman province, and the Hellenistic era effectively ended.
Other Civilizations Around the World
In the region of modern-day Israel, Herod the Great ruled as a client king under Rome from 37 to 4 BC, overseeing massive building projects including the expansion of the Second Temple in Jerusalem. In the Balkans, the Dacian king Burebista unified tribes across a wide territory from 82 to 44 BC, creating a kingdom powerful enough to concern Rome.
In Mesoamerica, the Maya were well into their Preclassic period. Their Long Count calendar, which tracked days from a mythical creation date of August 11, 3114 BCE, was already in active use. The basic cycle counted in units of 20 and 360 days, building up to a full cycle of 5,125 years. Maya cities were growing in complexity, with monumental architecture and early forms of writing developing across the Yucatán Peninsula and Guatemala.
What Came Before the 1st Century BC
If you’re thinking even further back, the 1st century BC sits at the very end of a long chain of human eras. The Stone Age lasted from roughly 3.3 million years ago to about 3000 BC, covering 99% of human existence. The Bronze Age followed, running from about 3000 BC to 1200 BC, when copper and tin alloys replaced stone as the primary material for tools and weapons. The Iron Age came next, from 1200 BC to roughly 500 BC in the Near East, ending when written historical records became widespread enough that archaeologists stop using material-based labels.
The 2nd century BC (200 BC to 101 BC) saw Rome destroy Carthage in the Third Punic War, the Seleucid Empire fragment across the Middle East, and the Han dynasty consolidate control over China. By the time the 1st century BC began, the political map was already dominated by the empires that would define the transition into the common era.
How Many People Were Alive
At the turn from 1 BC to AD 1, the United Nations estimates roughly 261 million people lived on Earth. For perspective, that’s smaller than the current population of Indonesia alone. The vast majority of those people lived in just three regions: the Roman Empire ringing the Mediterranean, the Han Empire in eastern Asia, and the Indian subcontinent. Large parts of sub-Saharan Africa, the Americas, and northern Europe were populated but at far lower densities, with societies organized around smaller tribal or city-state structures rather than centralized empires.