Kalniņš is the masculine form of a Latvian family name.
The surname may refer to:
Alfrēds Kalniņš, Latvian composer
Andis Kalninš, Mayor
Brūno Kalniņš, Latvian social democratic politician and historian
Eduards Kalniņš, Latvian general.
Gatis Kalniņš, Latvian striker
Harald Kalnins, German-Latvian bishop (see de:Harald Kalnins)
Imants Kalniņš, Latvian composer
Ivars Kalniņš, Latvian film and television actor
Jānis Kalniņš, Canadian composer, son of Alfreds
Jānis Kalniņš, Latvian ice hockey goaltender
Pauls Kalniņš, Latvian social democratic politician and four-time acting president
Rodrigo Kalniņš, Latvian actor
Rolands Kalniņš, Latvian film director
Pēteris Kalniņš, Latvian luger