Old Persian language in the context of "Dahae"

The Achaemenid Empire (/əˈkiːmənɪd/ ə-KEE-mə-nid; Old Persian: 𐎧𐏁𐏂, Xšāça, lit. 'The Empire' or 'The Kingdom') was an ancient Iranian empire founded by Cyrus the Great of the Achaemenid dynasty in 550 BC. At peak, its territorial extent was roughly 5.5 million square kilometres (2.1 million square miles), making it the largest empire of its time. Based in the Iranian plateau, it stretched from the Balkans and Egypt in the west to the Indus Valley in the east, including Anatolia, Cyprus, Mesopotamia, the Levant, parts of Eastern Arabia, and large parts of Central Asia.

By the 7th century BC, the region of Persis, located in the southwestern part of the Iranian plateau, had been settled by Persians. From Persis, Cyrus rose and defeated Media, Lydia, and the Neo-Babylonian Empire, thus marking the establishment of a new imperial polity in the ancient Near East. While its conquests were largely successful in most regions, the Achaemenid Empire's attempts to expand into Greece proved extremely difficult over the course of decades of wars and multiple kings, ultimately resulting in its defeat in the Greek mainland.

Sardis (/ˈsɑːrdɪs/ SAR-diss) or Sardes (/ˈsɑːrdiːs/ SAR-deess; Lydian: 𐤮𐤱𐤠𐤭, romanized: Sfar; Ancient Greek: Σάρδεις, romanized: Sárdeis; Old Persian: 𐎿𐎱𐎼𐎭, romanized: Sparda) was an ancient city best known as the capital of the Lydian Empire. After the fall of the Lydian Empire, it became the capital of the Persian satrapy of Lydia and later a major center of Hellenistic and Byzantine culture. Now an active archaeological site, it is located in modern day Turkey, in Manisa Province, near the town of Sart.

In 2025, Sardis was listed as UNESCO World Heritage Site.

Darius I (Old Persian: 𐎭𐎠𐎼𐎹𐎺𐎢𐏁 Dārayavaʰuš; c. 550 – 486 BCE), commonly known as Darius the Great, was the third King of Kings of the Achaemenid Empire, reigning from 522 BCE until his death in 486 BCE. He ruled the empire at its territorial peak, when it included much of West Asia, parts of the Balkans (Thrace–Macedonia and Paeonia) and the Caucasus, most of the Black Sea's coastal regions, Central Asia, the Indus Valley in the far east, and portions of North Africa and Northeast Africa including Egypt (Mudrâya), eastern Libya, and coastal Sudan.

Darius ascended the throne after overthrowing the Achaemenid monarch Bardiya (or Smerdis), who he claimed was in fact an imposter named Gaumata. The new king met with rebellions throughout the empire but quelled each of them; a major event of Darius's career described in Greek historiography was his punitive expedition against Athens and Eretria for their participation in the Ionian Revolt.

The Achaemenid dynasty (Old Persian: 𐏃𐎧𐎠𐎶𐎴𐎡𐏁𐎡𐎹 Haxāmanišyaʰ; Persian: هخامنشی Haxâmaneši; Ancient Greek: Ἀχαιμενίδαι Achaimenidai; Latin: Achaemenides) was a royal house that ruled the Achaemenid Empire, which eventually stretched from Egypt and the Balkans in the west to Central Asia and the Indus Valley in the east.

The Satrapy of Armenia (Old Persian: 𐎠𐎼𐎷𐎡𐎴, romanized: Armina or 𐎠𐎼𐎷𐎡𐎴𐎹, Arminiya), a region controlled by the Orontid dynasty (570–201 BC), was one of the satrapies of the Achaemenid Empire in the 6th century BC that later became an independent kingdom. Its capitals were Tushpa and later Erebuni.

Darius III (Old Persian: 𐎭𐎠𐎼𐎹𐎺𐎢𐏁 Dārayavaʰuš; Ancient Greek: Δαρεῖος Dareios; c. 380 – 330 BC) was the thirteenth and last Achaemenid King of Kings of Persia, reigning from 336 BC to his death in 330 BC.

Contrary to his predecessor Artaxerxes IV Arses, Darius was a distant member of the Achaemenid dynasty. During his early career, he was reportedly an obscure figure among his peers and first rose to prominence during the Cadusian expedition of Artaxerxes III in the 350s BC. As a reward for his bravery, he was given the Satrapy of Armenia. Around 340 BC, he was placed in charge of the royal "postal service," a high-ranking position. In 338 BC, Artaxerxes III met an abrupt end after being poisoned by the court eunuch and chiliarch (hazahrapatish) Bagoas, who installed Artaxerxes' youngest son Arses on the throne. He only reigned for a few years, until Bagoas had him poisoned as well. Darius was subsequently installed on the throne and soon forced Bagoas to drink his poison after discovering that the eunuch had planned to poison him as well.

The Twenty-seventh Dynasty of Egypt (notated Dynasty XXVII, alternatively 27th Dynasty or Dynasty 27), also known as the First Egyptian Satrapy (Old Persian: 𐎸𐎭𐎼𐎠𐎹, romanized: Mudrāya), was a satrapy of the Achaemenid Empire between 525 and 404 BC. It was founded by Cambyses II, the King of Persia, after the Battle of Pelusium (525 BC) and the Achaemenid conquest of Egypt, and his subsequent crowning as Pharaoh of Egypt. It was disestablished upon the rebellion and crowning of Amyrtaeus as Pharaoh. A second period of Achaemenid rule in Egypt occurred under the Thirty-first Dynasty of Egypt (343–332 BC).