In 2017, León was the first paid transfer in Spanish women's football history when she signed for Barcelona from Atlético Madrid, with a fee of 50,000 euros.

León previously played internationally with the Spanish national team, making her debut in 2016, in qualifiers for the 2017 UEFA Women's Euro.

[2] León was discovered by David Magaña, a former Zaragoza CFF sporting director, who noticed her and her brother Javi playing football while shopping in a Carrefour supermarket.

[4] In 2013, Zaragoza made it to the final of the Copa de la Reina, where they faced León's future club FC Barcelona.

[18] With a year remaining on her contract with Atlético Madrid, León signed for a fee of €50,000, becoming the first paid transfer in the history of Spanish women's football.

León kept a clean sheet for 120 minutes against her former club Atlético Madrid, as they won the match after a goal late in extra time.

[22] In 2019, León played the first Champions League Final of her career against Lyon, where Barcelona conceded four goals within the first 30 minutes of the match, and ultimately lost 1–4 against the European giants.

[29][30] In March 2021, she was suspended for four matches and fined €601 by the RFEF for criticising the quality of refereeing in the Primera Iberdrola after receiving a controversial red card against Real Madrid.

[31] Barcelona appealed the decision to the Administrative Tribunal of Sport (TAD), and León was able to play against second-place opponent Levante in their upcoming league match.

Barcelona made it to the 2021 UEFA Women's Champions League Final after defeating Paris Saint-Germain on an aggregate score of 2–1.

In the second leg of the semifinal, León's centerback partner Andrea Pereira picked up a yellow card and was suspended for the final.

[37] Barcelona's defence recorded a shutout as they won 4–0, the first UEFA Women's Champions League title in club history.

[39] Following the conclusion of the Champions League, León played each minute of the remaining semifinal and final of the 2021 Copa de la Reina.

[41] On 3 June 2023, Mapi played the entire match as Barcelona won 3–2 against VfL Wolfsburg in the final to win her second Women's Champions League title.

[46] León started all of Spain's matches at the 2019 FIFA Women's World Cup as they made it to the Round of 16, where they faced the United States.

In the 7th minute, she conceded a penalty after making contact with Tobin Heath in the box, which Megan Rapinoe scored to put the USA 1–0 up.

[48] The following year in July, León participated in the 2022 UEFA Women's Euro, where Spain were eliminated in the quarterfinals by eventual champions England.

In September, León joined 14 of her teammates in abstaining from national team call-ups, a decision that arose from a conflict between the 15 players and Spain's coach, Jorge Vilda.

[46] Former Atletico Madrid manager Ángel Villacampa, who aided her transition from leftback to centerback, has described León as having the perfect connection to Barcelona’s style, with her ability to distribute the ball up the pitch and her preference for playing in a high block.

[54] In the same interview, she spoke in disapproval of the 2018 FIFA World Cup being hosted in Russia due to anti-gay purges in Chechnya.