The Senate of the Republic, (Spanish: Senado de la República) constitutionally Chamber of Senators of the Honorable Congress of the Union (Spanish: Cámara de Senadores del H. Congreso de la Unión, is the upper house of Mexico's bicameral Congress.

After a series of reforms during the 1990s, it is now made up of 128 senators:

In a senatorial race, each party nominates two candidates who run and are elected together by direct vote. The party of the two candidates that won the second highest vote within the state or the Federal District then assigns a senator to occupy the third seat (first minority seat), according to the list of candidates that the party registered with the Federal Electoral Institute (IFE).

Senators serve six-year terms, running concurrently with the President of Mexico. Special elections are rare, as substitutes are chosen at every election.

The Senate is completely renewed every six years, since senators are barred from immediate reelection.

In Spanish, it is conventional to refer to each Legislature of the Senate by the Roman numeral of its term.

Mexico (ⁱ/ˈmɛksɨkoʊ/; Spanish: México, IPA: [ˈmexiko] ( listen)), officially the United Mexican States (Spanish:  Estados Unidos Mexicanos (help·info)), is a federal constitutional republic in North America. It is bordered on the north by the United States of America; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of Mexico. Covering almost two million square kilometres (over 760,000 sq mi), Mexico is the fifth largest country in the Americas by total area and the thirteenth largest independent nation in the world. With an estimated population of over 113 million, it is the eleventh most populous country and the most populous Spanish-speaking country. Mexico is a federation comprising thirty-one states and a Federal District, the capital city.

In Pre-Columbian Mexico many cultures matured into advanced civilizations such as the Olmec, the Toltec, the Teotihuacan, the Zapotec, the Maya and the Aztec before the first contact with Europeans. In 1521, Spain conquered and colonized the territory from its base in México-Tenochtitlan, which was administered as the Viceroyalty of New Spain. This territory would eventually become Mexico as the colony's independence was recognized in 1821. The post-independence period was characterized by economic instability, the Mexican-American War and territorial cession to the United States, a civil war, two empires and a domestic dictatorship. The latter led to the Mexican Revolution in 1910, which culminated with the promulgation of the 1917 Constitution and the emergence of the country's current political system. Elections held in July 2000 marked the first time that an opposition party won the presidency from the Institutional Revolutionary Party.

Fidel Alejandro Castro Ruz (Spanish: [fiˈðel ˈkastro]; born August 13, 1926) is a Cuban revolutionary and politician, having held the position of Prime Minister of Cuba from 1959 to 1976, and then President from 1976 to 2008. He also served as the First Secretary of the Communist Party of Cuba from the party's foundation in 1961 until 2011. Politically a Marxist-Leninist, under his administration the Republic of Cuba was converted into a one-party socialist state, with industry and business being nationalized under state ownership and socialist reforms implemented in all areas of society. On the international stage, he also served as the Secretary-General of the Non-Aligned Movement from 1979 to 1983 and 2006 to 2008.