Rome was an Empire for over 500 years. During this time there were over 140 different emperors!
Augustus: Augustus was the first emperor. He was Julius Caesar's adopted son. In 31 BCE, after 30 years of civil war, Augustus defeated Anthony and Cleopatra, and because the first emperor of ancient Rome. He called himself emperor because he knew the people would never accept the title of king. Meet Emperor Augustus - The First Roman Emperor
Nero: Nero was quite young when he became emperor. At first Nero was a very good emperor. Unfortunately, he slowly became insane. Emperor Nero was insane.
Trajan: Trajan was Spanish. He was the first Roman emperor who was not from Italy. Under Trajan, the empire reached its greatest size.
Diocletian: The Roman empire had grown too big to manage effectively so Diocletian split the empire into two pieces, the Eastern Roman Empire (which included the city of Rome) and the Western Roman Empire.
Constantine: Constantine converted to Christianity and became the first Christian Roman emperor. He ruled the Eastern Roman Empire. Byzantium, the capital city, was renamed Constantinople, in his honor.
Valens: Valens was not the last emperor of ancient Rome. There were a couple more after him who tried their best. Oddly, the last emperor of ancient Rome was named Romulus Augustus - Emperor Augustus. So the first and last emperors of ancient Rome were both called Emperor Augustus. Thanks to Valens' deal with the barbarians, which turned out to be a very bad deal for the western Roman empire, Rome was on its way out. The very bad deal - Emperor Valens & the Barbarians