Tilsit cheese or Tilsiter cheese is a light yellow semi-hard cheese, created in the mid-19th century by Prussian-Swiss settlers, the Westphal family, from the Emmental valley. The original buildings from the cheese plant still exist in Sovetsk, Russia, formerly Tilsit on the Neman River in East Prussia.

The same ingredients to make the cheese were not available as in their home country and the cheese became colonized by different molds, yeasts, and bacteria in the humid climate. The result was a cheese that was more intense and full flavored. The settlers named the cheese after Tilsit, the Prussian town they settled at.

Tilsiter has a medium-firm texture with irregular holes or cracks. Commercially produced Tilsiter is made from pasteurized cow's milk, ranges from 30 to 60 percent milk fat and has a dark yellow rind. Often flavoured with caraway seed and peppercorns, Tilsiter is a complement to hearty brown/rye breads and dark beers. It is a common table cheese, yet versatile. Tilsit can be eaten cubed in salads, melted in sauces, on potatoes, flans, or burgers.

Using the re-imported recipe, Tilsiter has been manufactured in Switzerland since 1893. Swiss Tilsiter is mainly produced in 3 varieties. A mild version (green label) is made from pasteurized milk, a more strongly flavoured one from fresh, unpasteurized milk (red label), and the yellow-labeled "Rahm-Tilsiter" is produced from pasteurized milk with added cream.