Parthia (اشکانیان, "Ashkâniân") (248 BC - 226 AD) was an ancient civilization that ruled in the northeast of Persia (modern-day Iran).The Parthians defeated one of the four kingdoms that arose after Alexander the Great, the Seleucids, and conquered most of the Middle East. It also controlled part of the Silk Road and had trade with both China and Rome, bridging East and West.
The Parthian empire helped revive the Achaemenid Empire and was the Eastern neighbor and rival of the Roman Empire for the second half of its existence. When warfare between the two giants would break out, the Romans would usually get the best of it and the Parthians respected Roman military capability. The Parthian empire occupied territory in present-day Iran, Iraq, Turkey, Armenia, Azerbaijan, Turkmenistan, Georgia, Afghanistan, Tajikistan, Pakistan, and Syria.
The term "Parthian" (PAR-thee-un) is from an interesting characteristic of the Parthian fighters, who would fire arrows from horseback while in retreat. Thus Parthian means "relating to, being, or having the effect of a shot fired while in real or feigned retreat" (Merriam-Webster dictionary). This is preserved in the term Parthian Shot.
The Parthian empire came to a close after a series of debilitating civil wars. They were conquered by Ardashir, who founded the Sassanid Empire, or Neo-Persian, on the ashes of the Parthian Empire after defeating the Parthians in the Battle of Ormuz and seizing their capital in 226.