The river that flows through Syria into Iraq and on to the Persian Gulf is the Euphrates River.
The river which bordered the eastern Persian Empire was the Indus.
The Tigris River empties into the Persian gulf
Euphrates River
Indus River.
The Euphrates River
The largest Iranian river that flows into the Persian Gulf is the KARUN RIVER which starts in the Zagros Mountains and winds its way, roughly parallel with the Iraqi Tigris River into the Persian Gulf via a delta in the Iranian portion of the Shatt al-Arab.
The Indus River.
The River Evrotas
The Persian Gulf.
No
The Euphrates river flows and ends in the Persian Gulf.