Diego Nicolás Fernández Castro (born 8 March 1998) is a Chilean footballer who plays as a midfielder.

He last played for O'Higgins.

[1] In 2022 and 2023, Fernández played for O'Higgins.

[2] Fernández represented Chile at under-17 level in the 2014 South American Games.

[3] He also was a member of the Chile U22 squad in the 2019 Toulon Tournament.