Same-sex marriage is legal in the Mexican state of Chiapas, following a ruling by the Mexican Supreme Court on 11 July 2017.
Various LGBT activist groups delivered documents to the executive and legislative branches of government and the State Board of Human Rights on 15 February 2012, recommending amendments to the marriage laws of Chiapas to comply with federal anti-discrimination provisions. On 29 November 2013, Diego Cadenas Gordillo, acting as a human rights activist, sent a bill to legalize same-sex marriage and reform the Civil Code and Civil Procedure of the state. The proposal was rejected on 13 December 2013, citing that "popular initiatives" must be supported by 1.5% of the electorate, or 50,500 voters. On 3 January 2014, an injunction was filed before a federal judge because of the refusal of Congress to act on the initiative. The judge denied the injunction against the Civil Code and an appeal was filed in the Twentieth Circuit Court. In November 2014, activist and lawyer Diego Cadenas Gordillo filed a request for formal intervention by the Inter-American Commission of Human Rights (IACHR), claiming that the state Legislature, Governor Manuel Velasco Coello, nor the State Commission of Human Rights had responded to the discriminatory laws banning same-sex marriage in Chiapas.
After clashes between the Mayor of Chilón and religious groups in January 2014, activists filed a complaint with the National Commission on Prevention of Discrimination (Conapred). On 27 March 2014, Deputy Alejandra Ruiz Soriano from the Party of the Democratic Revolution (PRD) filed an initiative to amend 19 articles of the Civil Code and 15 articles of the Code of Civil Procedure, to incorporate the concept of marriage as "the free union of two people for the community of life, where both respect, equality and mutual aid are sought." In addition, it also standardized the concept of cohabitation, disregarding a person's sexual preference.
On 25 September 2014, a collective injunction for the legalization of same-sex marriage was filed. On 3 March 2015, 51 couples won the right to marry as the state's Civil Code was deemed unconstitutional by the SCJN. On 26 March 2015, a document sent from the Chiapan Congress was publicised and denounced the ruling and asked for a review stating in their brief that same-sex marriage was unnatural while making comparisons of homosexual relationships to incest. The Chairman of the Board of Congress later denied the filing of the review stressing that only he has the power to make the request and insisting that he never signed any document regarding the issue. However, on 16 April 2015 the media revealed that the state's Judicial Council website received the request on 23 March 2015 and had already assigned a number to the case.