The tree nut used in the paste associated with Nutella is the hazelnut.
Nutella is an Italian sweetened hazelnut-and-cocoa spread made by Ferrero. Although it is often casually called chocolate spread, hazelnuts are a defining ingredient and give the product its characteristic roasted, nutty flavor. It is commonly spread on bread, pancakes and French crêpes.
The product grew from gianduja, a Piedmontese mixture of chocolate and hazelnuts. After postwar cocoa shortages made chocolate more difficult to produce, Italian confectioners increased the proportion of locally available hazelnuts. Ferrero introduced the first jar of Nutella in 1964.
A common mix-up is assuming Nutella is primarily a nut butter. Its major ingredients include sugar and palm oil, while hazelnuts make up a smaller proportion. The brand is therefore best described as a hazelnut cocoa spread, not pure hazelnut paste.