Palmyrene Empire
In the 260s, the Palmyrene king Odaenathus helped the Romans defeat the Persians (Sasanian Empire) and became, though nominally still Rome's vassal, the real ruler of Syria Palaestina and Rome's other holdings in the Near East. His widow Zenobia declared herself the Empress of the breakaway Palmyrene Empire but she was defeated by the Romans in 272.