The traditional Swedish Midsummer staple of pickled fish is herring.
Swedish Midsummer feasts commonly include pickled herring, boiled new potatoes, sour cream, chives, strawberries, and snaps. Herring is known in Swedish as sill or, in some regional contexts, strömming. It has long been important to Swedish foodways because it is abundant in the surrounding waters and can be preserved for storage.
Pickling made herring practical long before modern refrigeration. Salt, vinegar, sugar, onions, mustard, dill, and other seasonings produce many varieties, so “pickled herring” refers to a family of preparations rather than one single recipe. Different households and regions may serve several flavors on the same festive table.
Herring is also eaten at Christmas and other Swedish celebrations, so it is not exclusive to Midsummer. A common mix-up is surströmming, which is fermented Baltic herring with a famously strong odor. It is a distinct preparation and is especially associated with northern Sweden and late-summer eating, whereas ordinary pickled herring is the familiar Midsummer dish.
Swedish Midsummer is celebrated around the summer solstice, with dancing around a maypole and outdoor gatherings often accompanying the meal.