Year 175 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Scaevola and Lepidus (or, less frequently, year 579 Ab urbe condita). The denomination 175 BC for this year has been used since the early medieval period, when the Anno Dominicalendar era became the prevalent method in Europe for naming years.
Antiochus manages to oust Heliodorus and takes advantage of Demetrius' captivity in Rome to seize the throne for himself under the name Antiochus IV Epiphanes.
During this period of uncertainty in Syria, the Egyptian ruler, Ptolemy VI, lays claim to Coele Syria, Palestine, and Phoenicia, which the Seleucid king Antiochus III has previously conquered. Both the Syrian and Egyptian parties appeal to Rome for help, but the Roman Senate refuses to take sides.
Timarchus is appointed governor of Media in western Persia by Antiochus IV to deal with the growing threat from the Parthians while Timarchus' brother, Heracleides, becomes minister of the royal finances.
The construction of the western front of the altar in Pergamum, Turkey begins (approximate date) and is finished in 156 BC. A reconstruction of it is now kept at the Staatliche Museen zu Berlin, Preussischer Kulturbesitz, Pergamonmuseum in Berlin.