Rome’s Most Important Emperors


Almost 200 people have sat on the throne of the Roman Empire. Some were very good and you probably have heard of them already. Some were very bad and you probably have heard of them, as well. Most, however, were middling, forgettable, with short reigns that accomplished nothing of note. Today, we will be taking a look at the 10 among them who, arguably, had the most noteworthy and impactful reigns as emperor. 

The entries are in chronological order. Also, a quick mention on Julius Caesar – although he held the title of imperator, back then it was more of a military title and did not mean the same thing as our modern understanding of an emperor. He was a dictator, so he is not on the list, despite the giant impact he had on Roman history.

10. Augustus

Obviously, we are going to start with the first Roman Emperor, Augustus Caesar. Born Gaius Octavius in 63 BC, his reign marked the transition between the Roman Republic that lasted for almost 500 years and the beginning of the empire. 

He was the great-nephew of Julius Caesar, as well as his adopted son and heir. After Caesar’s assassination, Octavian allied himself with two of his uncle’s former allies, Mark Antony and Marcus Lepidus, and formed the Second Triumvirate to defeat their enemies, which was accomplished at the Battle of Philippi in 42 BC. Afterwards, the three members of the triumvirate each ruled different parts of the empire, but their ambitions got in the way of harmonious cooperation and soon fought each other for supreme power. Octavian came out on top and became Rome’s first emperor, even though he himself never used this title, instead preferring to call himself Augustus and Princeps and retaining the Senate to give an illusion of democracy even though, ultimately, he had control over all aspects of government.

If Augustus had turned out to be an ineffective ruler, then the empire might have ended as soon as it began and the Republic restored. But that was not the case. He reigned for over 40 years, time during which he almost doubled the size of the empire through military expansion. He founded the Praetorian Guard, enacted new social reforms and initiated numerous construction projects. He did a lot more than we can cover in this short entry, but he certainly put the Roman Empire on the path to domination, beginning a period of power and prosperity known as Pax Romana.

9. Nero

One could certainly argue that the emperors who followed Augustus such as Tiberius and Claudius, and even Caligula due to his notoriety, should be included on this list. But since we are limited to only ten emperors, we have to be a bit more selective and mention the ones who were there at pivotal moments in the history of the Roman Empire. That’s why we are jumping ahead a bit to the fifth emperor, Nero.

Nero is a name associated with debauchery and tyranny. He rose to the throne in 54 AD thanks to the machinations of his mother, Agrippina, and during the first part of his 13-year reign, he was content to sit back and indulge his vices while Agrippina, his tutor Seneca, and the Praetorian Prefect Burrus were actually in charge of the empire. 

This ended when Nero began fearing that his mother might be conspiring against him, intending to replace him with her stepson, Britannicus. Nero had them both killed, along with a bunch of other people, and this marked the beginning of his rule as a murderous tyrant.

The most famous event to happen during Nero’s reign was the Great Fire of Rome in 64 AD. Contrary to the popular saying, Nero did not fiddle while Rome burned, although he had been accused of Roman historians of starting the fire in order to make room to build his new palace, the Domus Aurea. One thing he did do was blame the fire on the Christians and have them persecuted. 

Ultimately, Nero made an enemy of everyone, and he committed suicide in 68 AD, since he probably would have been killed, anyway. But his death also marked the end of the Julio-Claudian Dynasty, the first imperial dynasty of Rome. Could the empire outlive it? Nero’s death triggered a civil war but, ultimately, the empire persevered, thanks mainly to one man and his name was…

8. Vespasian

The year 69 AD was a tumultuous time for the Roman Empire. After the death of Nero and the end of his bloodline, there was a power void which multiple men fought to fill. This event became known as the Year of the Four Emperors and, as its name implies, it saw four men quickly assume the imperial title in succession. 

When the year started, Galba was emperor. He was killed by the Praetorian Guard in January and replaced by Otho, recognized as new emperor by the Senate. He, however, had to contend with Vitellius, who had been proclaimed the new ruler by his troops and was marching to Rome with an army to claim the throne. Vitellius won in April and became the new emperor, while Otho committed suicide. 

Meanwhile, at the edges of the empire, Vespasian, who was a renowned and respected military commander, was busy fighting in the First Jewish-Roman War. Like with Vitellius, his loyal troops in Judaea proclaimed Vespasian the new emperor, as did the ones in Egypt and Syria. Being further away, it simply took him longer to reach Rome, but he did in October. Vitellius was killed and, in December, Vespasian was proclaimed the new Emperor of Rome.

Vespasian went on to rule for almost ten years, founding the Flavian Dynasty. Undoubtedly, his biggest accomplishment was bringing some much needed stability to the empire and prevent it from fracturing completely. As a bonus, Vespasian was also the one who began construction on Rome’s most famous landmark, the Colosseum, although it was finished during the reign of his son, Titus.

7. Trajan

We’re already moving on to the third dynasty of Rome, arguably also its best, known as the Nerva-Antonine Dynasty. It contained the so-called “Five Good Emperors,” a name which refers to the first five rulers from this dynasty who presided over a time of affluence and strength for Rome. 

The first one was Nerva, but we are going to focus on the second of the Five Good Emperors, called Trajan. He was a very successful soldier-emperor, who was responsible for the empire’s second-greatest military expansion, after that of Augustus himself. Under Trajan, the Roman Empire became larger than ever, having annexed Nabatea, Dacia, Armenia, and parts of Mesopotamia and turning them all into new Roman provinces.

Trajan ruled for almost 20 years, dying in 117 AD after falling ill while on campaign. The Senate deified him and proclaimed Trajan to be Optimus Princeps, or “the best emperor.” Even to this day, Trajan is usually mentioned in the same breath as Augustus when talking about the best rulers that Rome has ever had, with some even placing Trajan on a pedestal one step above the first emperor.

6. Hadrian

The only emperor on our list who succeeded the previous entry, Hadrian was the heir of Trajan and the third of the Five Good Emperors. He also had a long reign of over 20 years, and he spent most of that time building, repairing and strengthening his empire.

Hadrian’s rule was in stark contrast to that of his predecessor. He had almost no expansionist ambitions and he even abandoned most of the new land that Trajan spent his entire life conquering. Usually, losing territory is a sign of a poor ruler and Hadrian knew that this move was incredibly risky and would earn him enemies, but he was a pragmatist. Hadrian understood that Rome simply did not have the soldiers necessary to keep all the new provinces, and trying to do so would only stretch its resources to the point that they risked triggering revolts throughout the whole empire. Hadrian was content with simply improving the Roman Empire from within instead of expanding it.

He probably enacted more construction projects than any other emperor and we don’t just mean large-scale projects like Hadrian’s Wall, for example, but basic structures such as forts, garrisons, bath houses, and temples. His rule wasn’t particularly exciting, but it was exactly what the empire needed to counterbalance the previous expansionist reign of Trajan. 

Hadrian was followed by the final two of the Five Good Emperors: Antoninus Pius and Marcus Aurelius. They, too, had long reigns and were more interested in administrative and social matters rather than military ones. Combined, the three of them ruled for over 60 years of relative stability and prosperity, but all of that went away because they were followed by…

5. Commodus

An “important emperor” does not have to mean a good one. For better or worse, Commodus had a major impact on the history of Rome. His reign is considered to mark the end of Pax Romana, the end of the Roman golden age.

He was the son of Marcus Aurelius. He became emperor in 176 AD, first as co-ruler with his father, and then went solo in 180 when Aurelius died. At first, Commodus was simply incompetent. He would rather spend his time throwing lavish parties in his palace than fulfill his duties as emperor. Soon enough, most of his father’s trusted generals and senators lost their power and influence. They were replaced by Commodus’ sycophantic entourage, men who easily manipulated the young and foolish emperor in order to make themselves as rich and powerful as possible.

But with time, Commodus morphed into a murderous tyrant. He was the target of multiple conspiracies and he kept surviving them, but with each one, he became more paranoid and bloodthirsty. He had most of the people around him executed because he didn’t know who he could trust. Eventually, his luck ran out and Commodus was assassinated on December 31, 192 AD. 

He had no heirs so his death ended the Nerva-Antonine Dynasty and triggered a new civil war even worse than the one caused by Nero’s demise. As Cassius Dio put it, Commodus caused the Roman Empire to descend “from a kingdom of gold to one of iron and rust.”

4. Aurelian

We move forward to 235 AD, a year that marked the beginning of one of the most turbulent times for Rome, a period of major instability that lasted for 50 years and almost brought about the end of the empire, which was known as the Crisis of the Third Century.

There were multiple factors that caused this situation. Internally, Rome was simply not as strong or rich as it used to be. The empire had been ravaged by a plague in the second century, and would soon face another one between 249 and 262 AD. This left both the economy and the military in dire straits, as the previous Severan Dynasty had been forced to devalue its currency several times. Externally, Rome had to contend with numerous barbarian invasions, mainly from Germanic tribes, and it simply did not have the soldiers to keep them at bay, while simultaneously putting down all the revolts that were appearing throughout the empire as the result of disease, famine, and poverty.

Another major issue was the lack of stable leadership. The death of Severus Alexander in 235, which also ended his dynasty, also caused a civil war over who will become the new ruler. This led to the Year of the Six Emperors in 238 AD which, yes, meant that six men tried to claim the throne in a single year.

It wasn’t really a matter of all these problems eventually causing the empire to collapse. It had already begun. By 268 AD, two large chunks of the Roman Empire broke off and went on their own. To the west, we had the Gallic Empire, which included the provinces located in modern-day France, Britain, Germany, and Spain. And to the east there was the Palmyrene Empire, made up of the provinces of Egypt and Syria.

That is where Aurelian came in. He became Roman Emperor in 270 and won a large number of military victories that not only regained the former Roman provinces, but also managed to push back the invading Germanic tribes. For this, Aurelian was given the title Restitutor Orbis, or “Restorer of the World.” Unfortunately, Aurelian was assassinated after a short reign of five years, so he did not have time to end the crisis permanently. That task was left to…

3. Diocletian

After Aurelian’s death, the practice of short, unstable reigns resumed. Diocletian assumed the throne in 284, less than a decade after Aurelian, yet that was still time to include six other emperors between them. But then finally things changed with Diocletian, who had a long reign of over 20 years and finally brought an end to the Crisis of the Third Century.

Although a military man, Diocletian enacted reforms in every aspect of Roman government, even continuing some of the policies that Aurelian originally wanted to install. The biggest innovation, however, was implementing a new system of government dubbed the tetrarchy, or “rule of four.” He would rule half the empire, while another man named Maximian ruled the other. They were co-emperors, with the title of Augustus, but they each also appointed a junior co-emperor, with the lesser title of Caesar, who would also co-rule but, at the same time, also serve as their successors. The main goal here was to ensure a smoother transition of power when one of the Augustus died or abdicated.

The tetrarchy system did not last long, but it did reveal one step which was necessary to save the empire, one which would become permanent a few decades later, and that was splitting the Roman Empire into its eastern and western halves, with each side ruled by a different emperor. 

Overall, it’s hard to say if Diocletian was a good emperor. His tetrarchy didn’t work too well. His economic reform was a bust and he enacted the most violent persecution of Christians. However, his impact is undeniable, as his reign permanently changed the course of Roman history.

2. Constantine

The reason why Diocletian’s tetrarchy failed was because it was dependent on each co-ruler being happy with his role and, in real life, ambitions got in the way. Upon Maximian’s abdication, his junior Caesar, Constantius, assumed the senior role of Augustus, but when he died suddenly just a year into his reign, a new civil war broke out between multiple contenders.

The war was eventually won by Constantius’ son, Constantine, who went on to become one of the last true great rulers of the Roman Empire. His reign is sometimes seen as the transition point between the ancient Roman Empire and the one of the medieval era since Constantine brought so many changes that altered the direction of Roman history. 

Most notably, Constantine was the first Roman emperor to convert to Christianity, making it the new religion of the empire and spreading it throughout the whole of Europe. He also founded a new city on the site of the ancient settlement of Byzantium, and he named it after himself – Constantinople. This is also the reason why the Eastern Roman Empire would later be referred to as the Byzantine Empire by historians. 

Constantinople would become the new seat of power, and the capital of the Eastern Roman Empire, while Rome would become a mere shell of its former self, again another sign that the ancient times had passed. 

1. Justinian

For our last emperor, we travel to the 6th century AD. By this point, not only had the empire split into the western and eastern halves, but the Western Roman Empire had already stopped existing, being conquered and split into different kingdoms. But many Eastern emperors still believed in renovatio imperii romanorum, the “renewal of the empire of the Romans,” an idea that it was still possible to recapture what was lost and restore the empire to its former glory. Justinian was one of them and he got closer than anybody else to making that idea a reality.

With one of the longest reigns in Roman history at almost 39 years, Justinian had plenty of time to try and enact his ambitions. He spent most of his reign in military campaigns against the Sassanid Empire and the many Germanic nations such as the Ostrogoths, the Visigoths, and the Vandals who now controlled the former provinces of the Western Roman Empire. By the time he was finished, Justinian managed to regain a lot of the territory in the Mediterannean, including North Africa, Dalmatia, parts of the Iberian Peninsula, and, most importantly, Italy.

Inside his empire, Justinian was a prolific builder, his most famous contribution being the Hagia Sophia. He also enacted a new and influential code of law called the Corpus Juris Civilis, or simply the Code of Justinian, which formed the basis for many legal systems that came after it. In the end, Justinian did not fulfill all of his goals, but his reign was impactful enough that he was one of the few to be given the moniker of “Last of the Romans.”

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