Alexis Mac Allister is an Argentine professional footballer who plays as a midfielder for Premier League club Liverpool and the Argentina national team. He was part of Argentina world cup winning team in 2022.

Mac Allister started his senior career with Argentinos Juniors in 2016, winning the Argentine second division in his debut season. He joined Brighton & Hove Albion in 2019 but was immediately loaned back to them until the end of the season and later to rivals Boca Juniors, where he won the 2019–20 Primera División. Returning from the loan the following season, Mac Allister had his breakthrough year for Brighton, becoming a key player for the team, before moving to Liverpool in June 2023.

Alexis Mac Allister was born on 24 December 1998 in Santa Rosa, La Pampa. Mac Allister's older brothers Francis and Kevin are also footballers. They are the sons of Carlos Mac Allister and nephews of Patricio Mac Allister, both retired footballers. Mac Allister is of Irish descent, tracing his ancestry to Donabate, in County Dublin, Ireland. Mac Allister also has Italian ancestry through his maternal grandmother.

Soon after debuting for Argentinos, Mac Allister received a call-up from Claudio Úbeda for the Argentina under-20s. He was selected for the senior team for the first time in August 2019, ahead of friendlies in the United States in September versus Chile and Mexico. His international bow arrived in the match with Chile at the Los Angeles Coliseum on 5 September.

Mac Allister was recalled to the Argentina national team's senior squad in January 2022 after two and a half years since his first two caps. However, he tested positive for COVID-19 and missed Argentina's 2022 FIFA World Cup qualifier against Chile. He eventually made his first appearance for the national team for almost three years when he started in the 3–0 home win over Venezuela on 25 March. Five days later, in the draw with Ecuador he was forced off injured after being the victim of a knee-high challenge. Due to the subsequent injury, he was returned to Brighton ahead of their next fixture. On 1 June, Mac Allister was an unused substitute as Argentina beat Italy 3–0 in the 2022 Finalissima held at Wembley Stadium.