The LXIV Legislature of the Mexican Congress was the meeting of the Mexican Congress of the Union that convened on 1 September 2018 and ended on 31 August 2021. It is composed of the 500 federal deputies and 128 senators elected in the 2018 Mexican general election. While the deputies served only in the LXIV Legislature, the senators, elected to six-year terms, also formed the Senate in the LXV Legislature, which convened in 2021.

The LXIV Legislature is noteworthy for its gender parity, with the most women ever elected to the Chamber of Deputies and Senate. Women will hold 49 percent of the seats in the Senate, a national record and the third-highest percentage of women in a current national upper house, according to data collected by the Interparliamentary Union.^[1] The Chamber of Deputies will have the fourth-highest percentage of women among lower houses.^[2] In the Chamber of Deputies, this was the first election to be conducted after a 2017 redistricting of the federal electoral districts conducted by the National Electoral Institute. In reapportionment, Mexico City lost three seats, while seven states added a seat and four states lost one seat each.^[3] On August 23, the PRI, PRD, PAN and Movimiento Ciudadano announced they would challenge the allocation of proportional representation seats in the Chamber of Deputies, saying MORENA is overrepresented.^[4]