The move, confirmed by prime minister Hubert Minnis earlier, follows the continued increase in Covid-19 cases in a number of states.
Jamaica announced it would impose new restrictions on US travellers earlier.
The Bahamas order is effective as of Wednesday, at midnight.
In addition, Bahamasair will cease outgoing flights to the United States, effective immediately.
Outgoing flights will be permitted to accommodate any current visitors scheduled to return to the United States after Wednesday.
Private flights and charters from the United States, as well as pleasure craft and yachts will be permitted, and travellers from Canada, the United Kingdom and the European Union are exempt from the emergency order.
All visitors are required to present a negative Covid-19 RT-PCR test from a referenced lab, taken no more than ten days prior to the date of travel.
Since opening borders to international travel on July 1st, the Bahamas has experienced a deterioration in conditions relative to Covid-19.
These restrictions have been put in place to protect the health and wellbeing of both residents and visitors, which remains of primary importance, and to prevent the spread of the virus throughout the Bahamas, a statement explained.