In the 7th century BC, when Corinth was ruled by the tyrants Cypselus (r. 657-627 BC) and his son Periander (r. 627-585 BC), the city sent forth colonists to found new settlements: Epidamnus (modern day Durres, Albania), Syracuse, Ambracia (modern day town of Lefkas), Corcyra (modern day town of Corfu) and Anactorium. Periander also founded Apollonia (modern day Fier, Albania) and Potidaea (in Chalcidice). Corinth was also one of the nine Greek sponsor-cities to found the colony of Naukratis in Ancient Egypt. Naucratis was founded to accommodate the increasing trade volume between the Greek world and the pharaohnic Egypt, during the reign of Pharaoh Psammetichus I of the 26th dynasty.

Periander was one of the Seven Wise Men of Greece. During his reign the first Corinthian coins were forged. He was the first to attempt to cut across the Isthmus to create a seaway to allow ship traffic between the Corinthian and the Saronic Gulf. He abandoned the venture due to the extreme technical difficulties he met, but he created the Diolkos (a stone-build overland ramp) instead. The era of the Cypselids, ending with Periander's nephew Psammetichus, named after the hellenophile Egyptian Pharaoh Psammetichus I (see above), was the golden age of the city of Corinth.

Korinth, Stater, Korinth, Stater,

Korinth, Stater, Korinth, Stater, Korinth, Stater, Korinth, Stater,

During this era Corinthians developed the Corinthian order, the third order of the classical architecture after the Ionic and the Doric. The Corinthian order was the most complicated of the three, showing the accumulation of wealth and the luxurious lifestyle in the ancient city-state, while the Doric order was analogous to the strict and simplistic lifestyle of the older Dorians like the Spartans, and the Ionic was a balance between those two following the philosophy of harmony of Ionians like the Athenians. At this time there was a famous ancient saying: "Ou pantos plein es Korinthon", which translates as "Not everyone is able to go to Corinth", due to the expensive living standards that prevailed in the city. The city was renowned for the temple prostitutes of Aphrodite, the goddess of love, who served the wealthy merchants and the powerful officials living in or travelling in and out of the city. The most famous of them, Lais, was said to have extraordinary abilities and charged tremendous fees for her favours.

The city had two main ports, one in the Corinthian Gulf and one in the Saronic Gulf, serving the trade routes of the western and eastern Mediterranean, respectively. In the Corinthian Gulf lied Lechaion, which connected the city to it's western colonies (Greek: apoikoiai) and Magna Graecia, while in the Saronic Gulf the port of Kenchreai served the ships coming from Athens, Ionia, Cyprus and the rest of the Levant. Both ports had docks for the large war fleet of the city-state.

The city was a major participant in the Persian Wars, offering 40 war ships in the sea Battle of Salamis under the admiral Adeimantos and 5,000 hoplites (wearing their characteristic Corinthian helmets) in the following Battle of Plataea but afterwards was frequently an enemy of Athens and an ally of Sparta in the Peloponnesian League. In 431 BC, one of the factors leading to the Peloponnesian War was the dispute between Corinth and Athens over the Corinthian colony of Corcyra (Corfu), which probably stemmed from the traditional trade rivalry between the two cities.

After the end of the Peloponnesian War, Corinth and Thebes, which were former allies with Sparta in the Peloponnesian League, had grown dissatisfied with the hegemony of Sparta and started the Corinthian War against it, which further weakened the city-states of the Peloponnese. This weakeness allowed for the subsequent invasion of the Macedonians of the north and the forging of the Corinthian League by Philip II of Macedon against the Persian Empire. Philip's son Alexander the Great was the first general of the Hellenes.

In the 4th century BC, Corinth was home to Diogenes of Sinope, one of the world's best known cynics.