The LXVI Legislature of the Congress of the Union (66th Congress) is the current session of the legislative branch of Mexico, composed of the Chamber of Deputies and the Senate of the Republic. It convened on 1 September 2024, and will end on 31 August 2027, covering the final month of Andrés Manuel López Obrador's term in office and the first three years of Claudia Sheinbaum's presidency.
Both chambers of Congress were elected in the 2024 general election. There were three competing forces: the Sigamos Haciendo Historia coalition, consisting of the National Regeneration Movement (Morena), the Labor Party (PT), and the Ecologist Green Party of Mexico (PVEM); the Fuerza y Corazón por México coalition, comprising the National Action Party (PAN), the Institutional Revolutionary Party (PRI), and the Party of the Democratic Revolution (PRD); and the Citizens' Movement (MC), the only party to run without allies.
Sigamos Haciendo Historia won a supermajority in the Chamber of Deputies, granting the ruling coalition 73% of the seats, the highest share since the LII Legislature in 1982, during Miguel de la Madrid's presidency. Although the coalition fell three seats short of a supermajority in the Senate, defections by two senators elected for the PRD on 28 August closed the gap to one. The supermajority was ultimately secured with the defection to Morena of Cynthia López, elected for the PRI in Mexico City, on 12 November. This marked the first time since the LIII Legislature in 1985 that the ruling coalition held a supermajority in both chambers.
Major events
29 August 2024: Members-elect are sworn in. Gerardo Fernández Noroña is elected President of the Senate and Ifigenia Martínez y Hernández is elected President of the Chamber of Deputies for the first year of the legislature. 1 September 2024: Legislature convenes. 10 September 2024: Protesters opposing the judicial reform bill storm the Senate building, temporarily halting the session discussing the reforms. The Senate reconvenes in its former premises and passes the bill by an 86–41 vote at around 04:00 CST the following morning. 25 September 2024: The Senate voted 86–42 on a constitutional amendment that transfers the control of the National Guard to the Secretariat of National Defense. 1 October 2024: Claudia Sheinbaum becomes President of Mexico. 5 October 2024: President of the Chamber of Deputies Ifigenia Martínez y Hernández dies. 8 October 2024: Sergio Gutiérrez Luna is elected President of the Chamber of Deputies. 9 October 2024: The Senate unanimously approves a constitutional amendment aimed at ensuring that the minimum wage increases above inflation. 16 October 2024: The Senate unanimously approves a constitutional amendment that enables the State to reclaim the right to provide passenger train transportation. 16 October 2024: The Senate voted 86–39 on an energy reform bill that reestablishes the Federal Electricity Commission (CFE) and Pemex as public entities and mandates that the CFE retains a 54% share of electricity generation. 30 October 2024: The Chamber of Deputies voted 343–129 on a constitutional amendment that enshrines constitutional supremacy, allowing legal challenges to constitutional amendments only on procedural grounds. 12 November 2024: Morena and its allies secure a supermajority in the Senate with the defection of Cynthia López Castro. 12 February 2025: The Senate submitted the final list of candidates for the 2025 Mexican judicial elections to the National Electoral Institute (INE). 4 March 2025: The Chamber of Deputies voted 432–28 on a bill banning immediate reelection and prohibiting family members of current officeholders from seeking the same elected position. The reform is scheduled to take effect in 2030. 29 August 2025: Laura Itzel Castillo is elected President of the Senate for the second year of the legislature. 31 August 2025: The Chamber of Deputies postpones the renewal of its Board of Directors until 5 September amid Morena's rejection of PAN proposals; Sergio Gutiérrez Luna continues as President of the Chamber of Deputies. 2 September 2025: Kenia López Rabadán is elected President of the Chamber of Deputies for the second year of the legislature. 27 November 2025: The Senate approves the resignation of Attorney General Alejandro Gertz Manero in a 74–22 vote. 3 December 2025: The Senate compiled a list of ten finalists for the position of Attorney General, which the President narrowed to a shortlist of three. After the three finalists testified before the chamber, the Senate appointed Ernestina Godoy Ramos as Attorney General in a 97–19 vote.
Major legislation
Constitutional amendments +DOF CitationOfficial titleVotesPublishedDeputiesSenate15-09-2024A decree to amend, add, and repeal various provisions of the Political Constitution of the United Mexican States, regarding the reform of the Judicial Branch4 September 2024(357–130)11 September 2024(86–41)15 September 202430-09-2024A decree to amend, add, and repeal various provisions of the Political Constitution of the United Mexican States, regarding Indigenous and Afro-Mexican Peoples and Communities18 September 2024(483–0)24 September 2024(128–0)30 September 202430-09-2024A decree to amend and add Articles 13, 16, 21, 32, 55, 73, 76, 78, 82, 89, 123, and 129 of the Political Constitution of the United Mexican States, regarding the National Guard19 September 2024(353–126)24 September 2024(86–42)30 September 202430-10-2024A decree to amend the fourth paragraph and add a fifth paragraph to Article 28 of the Political Constitution of the United Mexican States, regarding railways and railway transportation8 October 2024(472–0)16 October 2024(123–0)30 October 202431-10-2024A decree to amend the fifth paragraph of Article 25, the sixth and seventh paragraphs of Article 27, and the fourth paragraph of Article 28 of the Political Constitution of the United Mexican States, regarding strategic areas and enterprises9 October 2024(350–111)16 October 2024(86–39)31 October 202431-10-2024A decree to amend the first paragraph of Section II of Article 107 and add a fifth paragraph to Article 105 of the Political Constitution of the United Mexican States, regarding the unchallengeability of additions or amendments to the Federal Constitution30 October 2024(343–129)24 October 2024(85–41)31 October 202415-11-2024A decree to amend and add Articles 4, 21, 41, 73, 116, 122, and 123 of the Political Constitution of the United Mexican States, regarding substantive equality, gender perspective, women's right to a life free of violence, and the elimination of the gender pay gap5 November 2024(468–0)24 October 2024(126–0)15 November 202402-12-2024A decree to amend and add Articles 4 and 27 of the Political Constitution of the United Mexican States, regarding well-being22 October 2024(408–65)30 October 2024(117–0)2 December 202402-12-2024A decree to amend and add Section XII of Subsection A of Article 123 of the Political Constitution of the United Mexican States, regarding housing for workers 23 October 2024(472–0)31 October 2024(103–0)2 December 202402-12-2024A decree to amend and add Articles 3, 4, and 73 of the Political Constitution of the United Mexican States, regarding animal protection and care 12 November 2024(441–0)21 November 2024(118–0)2 December 202420-12-2024A decree to amend, add, and repeal various provisions of the Political Constitution of the United Mexican States, regarding organizational simplification 20 November 2024(332–119)28 November 2024(86–40)20 December 202431-12-2024A decree to amend the second paragraph of Article 19 of the Political Constitution of the United Mexican States, regarding mandatory pretrial detention 13 November 2024(335–108)27 November 2024(93–35)31 December 202431-12-2024A decree to amend and add Article 21 of the Political Constitution of the United Mexican States, regarding public security 21 November 2024(441–0)13 November 2024(122–0)31 December 202417-01-2025A decree to add a fifth paragraph to Article 4 and a second paragraph to Article 5 of the Political Constitution of the United Mexican States, regarding health protection 3 December 2024(327–118)11 December 2024(86–39)17 January 202517-03-2025A decree to amend and add various provisions of Articles 4 and 27 of the Political Constitution of the United Mexican States, regarding the conservation and protection of native maize. 25 February 2025(382–88)5 March 2025(88–18)17 March 202501-04-2025A decree to add a second paragraph to Article 123 of the Political Constitution of the United Mexican States, regarding support for youth 25 September 2024(473–0)11 March 2025(112–0)1 April 202501-04-2025A decree to amend and supplement Articles 55, 59, 82, 115, 116, and 122 of the Political Constitution of the United Mexican States, regarding non-reelection and electoral nepotism 4 March 2025(432–28)25 February 2025(97–26)1 April 202501-04-2025A decree to amend the second paragraph of Article 19 and add second and third paragraphs to Article 40 of the Political Constitution of the United Mexican States, regarding the strengthening of national sovereignty 11 March 2025(327–116)26 February 2025(100–17)1 April 202515-04-2025A decree to amend the tenth paragraph of Article 25 and Subsection XXIX-Y of Article 73 of the Political Constitution of the United Mexican States, regarding administrative simplification and digitalization 19 March 2025(425–19)12 March 2025(107–3)15 April 2025
Budgets YearOfficial titleVotesPublishedTotal expendituresDeputiesSenate2025Law of Revenues of the Federation for the Fiscal Year 2025 26 November 2024(367–95)4 December 2024(84–36)19 December 2024MX$9.302 trillionBudget of Expenditures of the Federation for the Fiscal Year 2025 11 December 2024(349–129)24 December 20242026Law of Revenues of the Federation for the Fiscal Year 2026 15 October 2025(349–128)29 October 2025(80–37)7 November 2025MX$10.19 trillionBudget of Expenditures of the Federation for the Fiscal Year 2026 4 November 2025(358–133)21 November 2025
Party summary These tables relate to the composition of the Senate of the Republic and the Chamber of Deputies at the start of the LXVI Legislature and their current makeup, highlighting the changes in party affiliation that have occurred during the legislature.
Senate
PartyStart ofLegislatureCurrentseats±National Regeneration Movement6666National Action Party2221 1Ecologist Green Party of Mexico1314 1Institutional Revolutionary Party1513 2Labor Party66Citizens' Movement56 1Independents / No party12 1Total128128
Chamber of Deputies
PartyStart ofLegislatureCurrentseats±National Regeneration Movement257 3National Action Party71 2Ecologist Green Party of Mexico60 1Labor Party47 2Institutional Revolutionary Party36 1Citizens' Movement27 2Independents / No party1Party of the Democratic Revolution10 1Total500500
Leadership
Senate Board of Directors
The Senate's Board of Directors () is composed of a president, three vice presidents and four secretaries, elected by an absolute majority of the senators present in a ballot vote and serving one legislative year, with re-election permitted. For the second and third years it is chosen at a preliminary meeting held in the ten days before sessions open. The Senate has repeatedly gone beyond that statutory minimum, adding posts by parliamentary agreement so that every parliamentary group is represented: a fourth vice presidency and three further secretaryships in September 2024, and eight secretaries in 2025–2026.
2024–2025 The Senate elected its first Board of Directors on 29 August 2024, choosing Gerardo Fernández Noroña (Morena) as president in a ballot vote with 127 votes in favor and one against. On 3 September, the Senate approved an agreement of its Political Coordination Board adding, for that legislative year, a fourth vice presidency for the PVEM and three further secretaryships, allotted to Morena, the PAN and the PRI.