Onigiri, also known as Omusubi, is a snack of Japanese rice formed into triangle or oval shapes and often wrapped in nori (edible seaweed). Traditionally, the onigiri is filled with pickled ume fruit (umeboshi), salted salmon, katsuobushi, or any other salty or sour ingredient. In practice, pickled filling is used for preservation of the rice. Since the onigiri is one of the most famed and popular snacks in Japan, most convenience stores in Japan stock onigiri in many popular fillings and tastes. There are even specialized shops offering only handmade rice balls for take out.

Onigiri is not a form of sushi, despite common misconception. While onigiri is made with plain rice (lightly salted), sushi is made of rice with vinegar and sugar added. Onigiri is merely a method of making rice portable and easy to eat, while sushi originated as a way of preserving freshwater fish.

Onigiri are also found in many convenience stores in Taiwan and South Korea . In the latter, it is called samgak gimbap because of its triangular shape.