Bomba is the short-grain Spanish rice variety preferred for making paella. It is especially associated with the rice-growing regions of eastern Spain and Valencian cuisine, where paella developed.
Bomba grains absorb roughly two to three times their volume in liquid while retaining their shape. This makes them forgiving in a paella: the rice can take in saffron-rich stock and the flavors of meat, seafood, or vegetables without becoming as sticky as sushi rice or as creamy as risotto rice. Bomba is also known as Valencia rice, although “Valencia rice” can refer more broadly to rice from the region.
A common mix-up is Arborio, the Italian rice used for risotto. Arborio releases more starch and is intended to create a creamy texture, while paella traditionally aims for distinct, firm grains. Calasparra rice is another Spanish choice suitable for paella, but Bomba is the classic named variety in this question. Bomba is cultivated in areas including Calasparra and Moratalla, and protected examples may carry Spanish Denominación de Origen status.