A rollmop is a simple dish that is usually served as an appetizer. It's made of two main ingredients — a piece of fish and a vegetable. The fish is typically a fillet of herring that is pickled and rolled around a piece of vegetable — usually a pickle or onion. The pickled herring is held in place with a toothpick or small skewer. Rollmops originated in Germany, and while they can be homemade, they are also often purchased already assembled in jars.

While many traditional recipes only call for herring as the fish in a rollmop, any fish that is thin and pliable enough is acceptable. Alternatives to herring include smelt and other larger freshwater fish varieties. They can also be made with sardines though in Germany this variation comes by another name known as kronsardinen or crown sardines.

The pickled piece of fish is typically wrapped around another piece of food, usually a vegetable. It might be a pickle, such as a gherkin; a piece of onion, like a brown onion; or an olive, usually a green olive.

Rollmops are usually held together with a toothpick or skewer. More than one toothpick or skewer may also be used per piece to help hold everything together.

Rollmops may be made fresh, but they also come prepared in glass jars filled with pickled juice. They shouldn't be stored in metal containers because metal doesn't jive well with the acidic pickling solution the rollmops are submerged in. If rollmops are stored in an appropriate container and kept refrigerated, they typically remain edible and tasty for several weeks.

There are lots of ways to eat rollmops. Some eat them cold and with their hands, leaving the rollmop intact so the different flavors and textures can be experienced together. Others disassemble the ingredients and eat them as part of a sandwich, between two pieces of bread. Still others eat the ingredients of a rollmop separately, and some choose to coat them with bread crumbs and fry them in oil or bacon fat.

This dish was popular in 19th century Germany. Historical sources claim that Berlin was renowned for producing the best rollmops during that period. Their popularity has reportedly spread to many countries around the world and this dish continues to be enjoyed today.