Lisandro Martínez (born 18 January 1998) is an Argentine professional footballer who plays primarily as a centre-back for Premier League club Manchester United and the Argentina national team.

[4][5] He made his professional debut for Newell's in the club's final fixture of the 2016–17 season, when he played the full match in a loss to Godoy Cruz.

[15] His competitive bow came in the 2019 Johan Cruyff Shield against PSV Eindhoven, as Ajax won the trophy following a two-goal victory.

[16] Martínez netted his first Ajax goal on 28 September, as he opened the scoring in a 2–0 victory over Groningen at the Johan Cruyff Arena.

[20] On 7 August, Martínez made his club debut in a 2–1 home loss against Brighton & Hove Albion in the Premier League.

[21] However, after performances against rivals Liverpool and Southampton, he received the Manchester United Player of the Month award for August.

[25] On 29 September, Martínez reinjured his foot,[26] and was sidelined for four months, returning on 14 January 2024 as a substitute in Manchester United's 2–2 draw against Tottenham Hotspur.

[31] He became the first Manchester United player to score at their rivals' ground since Jesse Lingard in 2018, ending a drought of five league visits to Anfield without a goal.

[43] At the 2022 FIFA World Cup, Martinez came off the bench against Australia in the round of 16, making an important block on a shot by Aziz Behich.

[45] In the final against title-holders France, he was an unused substitute as Argentina won 4–2 on penalties to win their third World Cup title.

[47] He scored his first international goal, putting his team ahead in a 1–1 draw against Ecuador in the quarter-finals of the tournament, which ended with a victory in the penalty shootout.

[55] Before signing him, Ajax's scouts characterised Martínez as a left-footed ball-playing defender who is "tough as nails" and possesses winning mentality.