Adolfo Daniel Vallejo (born 28 April 2004) is a Paraguayan tennis player.
Vallejo has a career-high ATP singles ranking of 452 as of August 2023.
On the ITF Junior Circuit, Vallejo achieved a career-high junior ranking of No. 1, achieved in August 2022. This result came after a series of favorable results during the 2021 and 2022 season.
2021–2022 season
Beginning with his historical performance at the Junior Orange Bowl 2021 in Plantation, Florida, where he beat former junior world number 2, Bruno Kuzuhara to take the crown at this prestigious event. He is the first Paraguayan to achieve this and only the second to reach the final (the first being Victor Pecci).
Davis Cup
Vallejo represents Paraguay at the Davis Cup, where he has a win–loss record of 2–1.