Adolfo Daniel Vallejo (born 28 April 2004) is a Paraguayan tennis player.

[3] In 2021, he won the Junior Orange Bowl in Plantation, Florida, defeating Bruno Kuzuhara in the final.

He was the first Paraguayan player to win the tournament and only the second to reach the final after Víctor Pecci.

The following month, he won his first Challenger doubles title in Lima, Peru, partnering with Gonzalo Bueno, defeating Jorge Panta and Ignacio Buse in the final.

In March, he won his first Challenger title in São Léopoldo, Brazil, defeating Enzo Couacaud in the final.