Is it legal for my employer to keep my passport in Bahrain?

Your passport belongs to you. The LMRA's official guidance tells workers to keep their passport in their own possession and not to give it to anyone unless they fully agree and consent to the employer keeping it. If your employer has taken your passport and will not return it, ask for it back in writing first. If they refuse, contact the LMRA Expat Protection Centre on 17506055, which can intervene in cases where documents are being held, and can help you file a case. The Bangladesh Embassy labour wing can also help. Keep copies of your passport photo page and visa saved separately, so you always have your details even if the original is held.