Steven Diez (Spanish: Díez,[1] pronounced [ˈdi.eθ]; born March 17, 1991) is a Canadian professional tennis player.

Raised primarily in and competing for Spain early in his career, he has since gone on to represent the country of his birth, Canada, in the Davis Cup.

[3] Diez competed in the main draw of two senior level ITF Futures tournaments in the autumn, losing both times in the first round.

In late April he competed in qualifying for an ATP World Tour event, the 2008 Torneo Godó, losing in the first round to Marc López.

In July in consecutively played Futures he won his first-round match, but he failed, in singles, to reach the second round in his last five events of the year.

In June, he competed in his first main draw in an ATP Challenger, as a wild card entrant at the 2009 Open Diputación Ciudad de Pozoblanco, and reached the quarterfinals, where he lost to eventual runner-up, Thiago Alves.

The following week Diez captured his first tour title, that of Spain F23 in singles, defeating David Canudas-Fernandez in the final.

His singles wins stopped there as he won only one further tour main draw for the remainder of the year while losing eight.

Diez did not win a singles main-draw match in his first five events of the year leading into a call-up of sorts by Tennis Canada to represent the country of his birth in the Davis Cup.

He won a set from Michael Russell, before falling in the first round of qualifying for the 2010 Rogers Cup in Toronto, in early August.

After 15 attempts at qualifying at a major, he finally made his Grand Slam debut at the 2020 French Open.