Lisandro Martínez (লিসান্দ্রো মার্তিনেস) is an Argentine professional footballer who plays primarily as a centre-back for Premier League club Manchester United and the Argentina national team. Nicknamed "The Butcher", he is known for his aggressive style of play and accurate long passes from the back.

Martínez began his career at Newell's Old Boys before joining Defensa y Justicia in 2017, initially on loan. He signed for Ajax in 2019, where he made 120 appearances over three seasons and won two Eredivisie titles and one KNVB Cup. He won the Ajax Player of the Year award in the 2021–22 season.

Martínez won four caps for the Argentina under-20 team at the 2017 South American Youth Football Championship in Ecuador. The first came during the first stage against Venezuela, while the other three arrived during the final stage as Argentina finished fourth place and subsequently qualified for the 2017 FIFA U-20 World Cup in South Korea. He received a call-up for the U-20 World Cup but failed to make an appearance, appearing on the substitutes bench once against Guinea. Martínez made one appearance for Argentina at under-23 level, in a 5–0 friendly victory against Bolivia in September 2019.

In March 2019, Martínez received his first call-up to the senior team. He debuted against Venezuela on 22 March in Madrid. Martínez made one appearance at the 2021 Copa América, which Argentina won. He was an unused substitute in Argentina's 3–0 victory over Italy in the 2022 Finalissima. 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. Martinez was part of the starting XI against Netherlands in the quarter-finals and came off the bench against Croatia in the semis. 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.

He is primarily a centre-back, though he is capable of playing at left-back and as a defensive-midfielder, having played there at times for Defensa y Justicia and Ajax. He is a ball-playing centre-back and is known for his range of passing and composure on the ball. In the 2021–22 Eredivisie season, he averaged more passes per 90 minutes than any other player. Before signing him, Ajax's scouts characterised Martínez as a left-footed ball-playing defender who is "tough as nails" and possesses winning mentality. At Manchester United, his performances earned him comparisons to legendary former United defender Nemanja Vidić, with Vidic himself praising Martínez for his aggressive defending and leadership. Despite his relatively short stature for a defender, standing at 5'9", he is also effective in duels.