Tuna salad is typically a blend of two main ingredients: tuna

Tuna

Tuna is a salt water fish from the family Scombridae, mostly in the genus Thunnus. Tuna are fast swimmers, and some species are capable of speeds of . Unlike most fish, which have white flesh, the muscle tissue of tuna ranges from pink to dark red. The red coloration derives from myoglobin, an...

 and mayonnaise

Mayonnaise

Mayonnaise, , often abbreviated as mayo, is a sauce. It is a stable emulsion of oil, egg yolk and either vinegar or lemon juice, with many options for embellishment with other herbs and spices. Lecithin in the egg yolk is the emulsifier. Mayonnaise varies in color but is often white, cream, or pale...

 or mayonnaise-substitute. Chopped hard-boiled egg, celery

Celery

Apium graveolens is a plant species in the family Apiaceae commonly known as celery or celeriac , depending on whether the petioles or roots are eaten: celery refers to the former and celeriac to the latter. Apium graveolens grows to 1 m tall...

 or relish

Relish

A relish is a cooked, pickled, or chopped vegetable or fruit food item which is typically used as a condiment.In North America, relish commonly alludes to sweet pickle relish-like sauce that often condiments hot dogs, hamburgers and other types of fast food.-Description and ingredients:The item...

, and onion

Onion

The onion , also known as the bulb onion, common onion and garden onion, is the most widely cultivated species of the genus Allium. The genus Allium also contains a number of other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion The onion...

 are ingredients that are often added. Tuna salad is regularly served on top of lettuce

Lettuce

Lettuce is a temperate annual or biennial plant of the daisy family Asteraceae. It is most often grown as a leaf vegetable. It is eaten either raw, notably in salads, sandwiches, hamburgers, tacos, and many other dishes, or cooked, as in Chinese cuisine in which the stem becomes just as important...

, tomato

Tomato

The word "tomato" may refer to the plant or the edible, typically red, fruit which it bears. Originating in South America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler...

, avocado

Avocado

The avocado is a tree native to Central Mexico, classified in the flowering plant family Lauraceae along with cinnamon, camphor and bay laurel...

, or some combination of these. The tuna used is usually pre-cooked, canned, and packaged in water or oil.

Quick homemade tuna salad is often made by omitting the eggs and adding sweet relish. The reason for the change is that the eggs must be cooked whereas the other ingredients are purchased ready to eat. When the spread is placed on bread, it makes a tuna salad sandwich.

In Belgium, the dish pêches au thon / perziken met tonijn is made from halved canned or fresh peach

Peach

The peach tree is a deciduous tree growing to tall and 6 in. in diameter, belonging to the subfamily Prunoideae of the family Rosaceae. It bears an edible juicy fruit called a peach...

es stuffed with tuna salad.