Antigonus I Monophthalmus (382 B.C. - 301 B.C.) was a high-ranking general of the Macedonian Army of Alexander the Great, the Satrap of Phrygia after the Macedonian King's death in 323 B.C in Babylon and one of Alexander's Diadochi (Successors) who was the first to proclaim himself King in 306 B.C after the murder of Alexander's young son by the same name in 309 B.C. He ruled an Empire that consisted of Asia Minor and Syria until his death in the Battle of Ipsus in 301 B.C at the old age of 81. His epithet, Monopthalmus, (One-Eyed) refers to the fact that, after his youth, he had only a single eye.
Antigonus was also a high-ranking general under Alexander's Father, Philip II of Macedon. When his son ascended to the throne, Antigonus followed the young Macedonian King on his war against Persia. After the Battle of the Granicus in 334 B.C, he was appointed as Satrapy of Phrygia, a region in Asia Minor.
At the age of 32, Alexander the Great died in 323 B.C in Babylon without leaving plans for the dispensation of his vast Empire, which stretched from Macedon (north of Greece) to India, and included Egypt and all of modern-day Iraq. Thus, it fell to Alexander's friends and generals to manage the Empire who soon became divided over the succession to the Macedonian throne and what was to happen to the Empire itself, forming factions against each other. They shortly divided the Empire in the Partition of Babylon in 323 B.C. The partition assigned the Satrapies of the Macedonian Empire to many of Alexander's companions, generals as well as others.
However, Antigonus, and other generals, proved unable to work together, due to personal rivalries and greed. The generals and companions of Alexander went into war with each other, each administering an individual portion of the Empire in the name of Alexander IV. For example, Egypt fell to Ptolemy, who went on to call himself Pharaoh Ptolemy I Soter ("The Savior"). Antigonus and his subsequent dynasty took control of Macedon, Alexander's former home, and his ancestral kingdom.
Early in the division of the Empire, the Diadochi thought of themselves of keeping custody of the territories until they could be surrendered to Alexander's young son. However, when Alexander's son died, Antigonus crowned himself King, and crowned his son Demetrius as Co-King. Taking advantage of the victory at Salamis to use as a pretext to become King.
Shortly thereafter, relations between the Diadochi deteriorated further, and war broke out between the former friends. These wars - the "Wars of the Diadochi" - form the backdrop of the Hellenistic Era, and lasted until the ascendancy of Rome.
An old man, Antigonus did not live to see what would become of his dynasty after the defeat at Ipsus. However, his family would rule for some time to come. Managing to take over Antigonus's homeland of Macedonia and continually clashing with the other Diadochi, especially the Ptolemies. For example, his son Demetrius fought many wars against Ptolemy I, ultimately earning him the title "Poliorcetes" (Besieger of Many Cities).
In fact, one of the wonders of the Ancient World, the Colossus at Rhodes, was erected to honor Ptolemy after he defeated Demetrius in a pitched battle for the city of Rhodes.