The SS Mongolia was a steam turbine-driven twin-screw passenger-and-cargo ocean liner launched in 1922 for the Peninsular and Oriental Steam Navigation Company (P&O) for service from the United Kingdom to Australia. Later in P&O service she sailed for New Zealand, and in 1938 she was chartered to a P&O subsidiary, the New Zealand Shipping Company, as SS Rimutaka.

Mongolia
In 1950 she was sold to become the SS Europa, carrying immigrants to the United States from Europe; later, she became a Bahamas cruise ship, the SS Nassau. Its final incarnation was under a Mexican flag as a Los Angeles to Acapulco cruise liner, SS Acapulco, making her the only ocean liner to ever fly the Mexican flag. The ship was scrapped in 1964.

P&O was an important mail carrier and they tended to have the faster ships. They took priority in ports so that mail could be unloaded quickly.

The following illustrations show the ship and some interiors. These form part of the Letter Card.