Lactobacillus helveticus is a lactic-acid producing rod shaped bacterium of the genus Lactobacillus. It is most commonly used in the production of American Swiss cheese and Emmental cheese but is also sometimes used in making other styles of cheese, such as Cheddar, Parmesan, romano, provolone, and mozzarella. The primary function of L. helveticus culture is to prevent bitterness and produce nutty flavors in the final cheese. In Swiss and Emmental cheese production, L. helveticus is used in conjunction with a Propionibacter culture, which is responsible for developing the holes (known as "eyes") through production of carbon dioxide gas.

Ingestion of powdered milk fermented with L. helveticus was shown to decrease blood pressure due to the presence of manufactured tripeptides that have ACE inhibitor activity. However, there have been several contradictory results in later studies.

The bacterium's specific name is an adjective derived from "Helvetia", the Latin name for the region occupied by the ancient Helvetii .