Leonardo Martín Mayer[2] (Spanish: [leoˈnaɾðo maɾˈtim ˈmaʝeɾ],[a] German: [ˈmaɪɐ]; born May 15, 1987) is a tennis coach and a former professional player from Argentina.

[1] As a junior, Mayer won the 2005 French Open Boys' Doubles and the Orange Bowl with Emiliano Massa, reaching as high as No.

[1] Mayer qualified for his first Grand Slam at the 2009 French Open and beat 15th seed James Blake in straight sets in the first round.

[3] In February 2014, Mayer reached his first career ATP final at Viña del Mar, defeating second seed Tommy Robredo en route.

25 seed Andreas Seppi, former Wimbledon semifinalist and Australian Open runner-up Marcos Baghdatis, and Andrey Kuznetsov before being defeated by Grigor Dimitrov in straight sets.

Then, he played at the 2014 International German Open, where he beat Guillermo García López and Philipp Kohlschreiber, reaching the final without dropping a set.

In the doubles tournament, he partnered with compatriot Carlos Berlocq and made it to the quarterfinals, beating the reigning Wimbledon champions Jack Sock and Vasek Pospisil.

Mayer won his two singles rubbers against Israel in the Davis Cup Play-offs, helping Argentina to secure a place in the 2015 World Group.

On March 8, 2015, he played in the longest singles match in Davis Cup history, beating João Souza in 6 hours and 42 minutes, 7–6(7–4), 7–6(7–5), 5–7, 5–7, 15–13.

In the Open de Nice Côte d'Azur, he reached the third ATP final of his career, losing to Dominic Thiem.

He had minor success in the 2016 Indian Wells Masters beating Sam Groth and 20th seed Viktor Troicki before losing to Marin Čilić in the third round.

In July he lost in the 2nd round of qualifying to a teenager in the 2017 German Open only to enter the MD as lucky loser and win his first tournament as a father (his son Valentino was born in February 2017).

[4] Defeated 3 players ranked outside Top 100 to reach ATP Masters 1000 Indian Wells 4R (lost to his boyhood friend and eventual champion Juan Martín del Potro in 3 sets).

Fell to A. Zverev in ATP Masters 1000 Madrid 3R, but earned only break point faced by German en route to title.

Mayer reached the semifinals of a Grand Slam in doubles for the first time in his career at the 2019 Australian Open partnering João Sousa.