Family name Mills-Ostwald (Mills-Ostwald 
) , all over the world, is an extremely rare cognomen. The family name Mills-Ostwald is habitual in Northern America, particularly the United States, where it is an extremely rare surname. Parts of the name also exists independently as a last name Mills, and a last name Ostwald.
| VARIANT | COUNTRY |
|---|---|
| Mills-Ostwald | United States |