Gaius Plinius Secundus - or, to use his English name, Pliny - was born in 23 or 24BC at Novum Comum (modern Como), a small city in the region known as Gallia Transpadana. We do not know much about his family, except for the fact that he had a sister, and that his father was wealthy enough to be a member of the equestrian class, which means that he possessed at least 400,000 sesterces (100,000 normal day wages).

Much of the family history and Pliny's early life is provided by his nephew, Pliney the Younger. Pliny was the son of an equestrian, Gaius Plinius Celer, and his wife, Marcella. Neither the younger nor the elder Pliny mention the names. Their ultimate source is a fragmentary inscription found in a field in Verona and recorded by the 16th-century Augustinian monk Onofrio Panvinio at Verona.

As a result of his fathers wealth, Pliny the Elder was able to study, and in the 30's he was in Rome. Like al Roman boys, Pliny had to study rhetoric, which is essentially the art to speak in public. However, since a speech is only convincing when the speaker looks reliable, there was a lot more to rhetoric than only speaking: it was a complete program of good manners and general knowledge.

After 37, Pliny's teacher was Publius Pomponius Secundus, who was regarded as the best tragic poet of his age, and sometimes stayed at the imperial court of Caligula and Claudius. At the age of 15, he observed Lollia Paulina, the emperor's wife, at a wedding. Pliny considered Caligula's wife a parvenue. He wrote:

"I have seen Lollia Paulina celebrating her betrothal covered with alternating emeralds an pearls, which glittered all over her head, hair, ears, neck and fingers, to the value of 50 million sesterces. She was ready, at the drop of a hat, to give written proof of her ownership of the gems."

Pliny was a teenager, aged between 14–18, during the short reign of Caligula, considered insane by his contemporaries. He says that he saw the construction of the impious Palace of Caligula (it joined the Palace of Tiberius to the Temple of Castor and Pollux, where Caligula posed as a god).

In 46BC at age 23 Pliny entered the army as a junior officer, as was the custom for young men of equestrian rank. Pliny left Italy and went to Gallia Belgica, where he served as military tribune. Pliny's interest in Roman letters attracted the attention and friendship of other men of letters in the higher ranks, with whom he formed lasting friendships. Later these friendships assisted his entry into the upper echelons of the state; however, he was trusted for his knowledge and ability as well.

Pliny, developed a liking of the military, and was soon promoted to prefect of a cavalry unit. He was a fighting officer. His unit was stationed at Xanten (Castra Vetera) in Germania Inferior on the Lower Rhine. One day, he must have lost the bridle of his horse, because after many centuries, it was found by archaeologists.

According to his nephew, it was during this period that he wrote his first book (perhaps in winter-quarters when spare time was more abundant), a work on the use of missiles on horseback, De jaculatione equestri. It did not survive but in Natural History he seems to reveal at least in part its content: using the intelligence of the horse to assist the javelineer to throw missiles from its back. During this period also he dreamed that the spirit of Drusus Nero begged him to save his memory from oblivion. The dream prompted Pliny to begin forthwith a history of all the wars between the Romans and the Germans, which he was not to complete for some years.

The 'Natural History', which was dedicated to Titus in 77BC, was, according to the author's nephew, "a learned and comprehensive work as full of variety as nature itself". The same sentiment is expressed in the last line of the encyclopedia:

Greetings, Nature, mother of all creation, show me your favor in that I alone of Rome's citizens have praised you in all your aspects.

He deals with the entire creation, which is, in the author's stoic view fundamentally good because it is made by God. Another aspect of this encyclopedia that may cause some surprise to the modern reader, is the use of the word "history", which does not mean that Pliny is interested in the past (although he is), but means "research". The Latin title Historia naturalis could best be translated as "Research of the creation".

The encyclopedia utilizes some material from his memories of earlier times and from his prior works, such as the book on Germany. There is no evidence that he had planned to use this material in an encyclopedia later in his career. Most of the references in the encyclopedia must have come from his extracts, which he kept on an ongoing basis, hiring a reader and a secretary to keep them, and furnishing that secretary with gloves in winter so that his writing hand would not stiffen with cold. The extracts collected for this purpose filled rather less than 160 volumes, which Larcius Licinus, the praetorian legate of Hispania Tarraconensis, vainly offered to purchase for 400,000 sesterces. That would have been in 73/74 (see above). At his death Pliny left the 160 volumes to his nephew. When composition began is unknown. Since he was preoccupied with his other works under Nero and then had to finish the history of his times, it is unlikely he began before 70. The procuratorships offered the ideal opportunity for an encyclopedic frame of mind. The date of an overall composition cannot be assigned to any one year. The dates of different parts must be determined, if they can, by philological analysis (the "post-mortem" of the scholars).

Pliny the Elder died on August 25, 79BC, while attempting the rescue by ship of a friend and his family from the eruption of Mount Vesuvius that had just destroyed the cities of Pompeii and Herculaneum. The prevailing wind would not allow his ship to leave the shore. His companions attributed his collapse and death to toxic fumes, but they were unaffected by the fumes, suggesting natural causes.