Quark cheese, also called curd cheese, is a type of soft, white, un-aged cheese originating in Central Europe. Quark cheese is similar to other un-aged cheeses, such as farmer's cheese, French fromage frais, South Asian paneer, and Mexican queso blanco. Quark is typically low fat and a good source of protein and Vitamin B₁₂. It has been enjoyed by Germanic people since at least the first century CE, when Roman author Taciturn described it in his writings.

Quark cheese is acid set, meaning that it is the addition of lactic acid bacteria that turns the milk into cheese. The milk used to make quark must be pasteurized in the United States, as the cheese is not aged before it is eaten. Quark cheese is traditionally made without rennet, an enzyme complex naturally found in the mammalian stomach and used in much cheese production. However, some quark cheese is made with rennet, which results in a firmer product. Other variations add cream, spices, or fruit to the mixture.

When quark cheese is made with rennet, most or all of the whey, the liquid component left over in cheese production, is drained off. Traditionally, the cheese is hung in a porous cheesecloth, allowing the whey to drip out as the cheese forms. This process creates a wedge-shaped cheese. Today, the whey may be removed from quark cheese with a centrifuge in a factory.

Quark varies in firmness depending on how it is made, and different types are suited to different culinary uses. Rennetless quark, common to Germany, is very soft, similar in texture to sour cream, though slightly drier. It is continually stirred during production and sold in tubs with most of the whey remaining. This type of quark may be used as a spread, served with fruit, or used to make cheesecake.

In Eastern Europe, quark is drier and firmer and may be used in salads and sandwiches or to make cheesecake. This type of quark is sold in Canada as baking cheese. Quark cheese is not common outside of Central and Eastern Europe. Some dairies in the United States make it, but it is not easy to find.