Porphyry believed Plotinus was 66 years old when he died in the second year of the reign of the emperor Claudius, and estimated the year of his teacher's birth as around AD 205. Plotinus disliked "being in the body", so he never discussed his ancestry, or his place or date of birth. Eunapius however reports that he was born in Lyco or Lycopolis in Egypt.
He took up the study of philosophy at the age of 27, around the year 232, and went to Alexandria to study. Plotinus was dissatisfied with every teacher he met until a friend suggested he go to Ammonius Saccas. Upon hearing Ammonius lecture, he declared to his friend "This was the man I was looking for," and began to study intently under this teacher. Plotinus spent the next eleven years in Alexandria until his 38th year, when he decided to investigate the philosophical teachings of the Persians and the Indians. As a result he left Alexandria and joined the army of Gordian III as it marched on Persia. However, on Gordian's death he found himself abandoned in a hostile land, and with difficulty found his way back to safety in Antioch.
At the age of 40, during the reign of Philip the Arab, he came to Rome, where he lived for most of the remainder of his life. He attracted a number of students in that city. His innermost circle included Porphyry, Gentilianus Amelius of Tuscany, the Senator Castricius Firmus, and Eustochius of Alexandria -- a doctor who devoted himself to learning from Plotinus and attended to him until his death.
Others included: Zethos, an Arabian by ancestry who died before Plotinus and left him a legacy and some land; Zoticus, a critic and poet; Paulinus, a doctor of Scythopolis; and Serapion from Alexandria. He had students amongst the Roman Senate beside Castricius, such as Marcellus Orontius, Sabinillus, and Rogantianus. Women were also numbered amongst his students, including Gemina, in whose house he lived during his residence in Rome, and her daughter Gemina; and Amphiclea, the wife of Ariston the son of Iamblichus. He was a correspondent of the philosopher Cassius Longinus.
He also had the respect of the Emperor Gallienus and his wife Salonica. At one point Plotinus attempted to interest the Emperor Gallienus in rebuilding an abandoned settlement in Campania known as the City of Philosophers, where the inhabitants would live under the constitution set out in Plato's Laws. The support of an Imperial subsidy did not come to pass due to reasons Porphyry did not know, and the settlement never happened.
After Porphyry went to live in Sicily, word came to him that Plotinus had died. The philosopher spent his final days in seclusion on an estate in Campania which his friend Zethus had bequeathed him. According to the account of Eustochius, who attended upon at the end, Plotinus' final words were: "Strive to give back the Divine in yourselves to the Divine in the All." At that moment a snake crept under the bed Plotinus lay, and slipped away through a hole in the wall; at the same moment Plotinus died.
Besides Ammonius, Plotinus was greatly influenced by the works of Alexander of Aphrodisias and Numenius.
Porphyry wrote the essays that became the Enneads over a period of years, from c.253 to a few months before his death. Plotinus was unable to revise his own work due to his poor eyesight. Yet his writings badly needed editing, according to Porphyry: Plotinus' handwriting was atrocious, he did not properly separate his words, and he cared nothing for spelling. He disliked the process of rewriting them, so he gave the task to Porphyry, who not only polished them but put them into the arrangement we now have them.
Plotinus taught the existence of an indescribable One, which emanated the rest of the universe as a sequence of lesser beings. Later Neo-Platonic philosophers, especially Iamblichus, added hundreds of intermediate gods and beings as emanations between the One and humanity; but Plotinus' system was much simpler in comparison.