Cognomen Mlačnik (Mlačnik 
) , throughout the world, is a very rare family name. The surname Mlačnik is habitual in Southern Europe, particularly Slovenia, where it is quite a rare surname.
| VARIANT | COUNTRY |
|---|---|
| Mlačnik | Slovenia |
| edvard mlačnik Slovene military personnel, SI (b. 1954) |
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| vid mlačnik SI |
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| jure mlačnik SI |
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| primož mlačnik SI (b. 1990) |
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