Los TECOS is a Mexican secret society associated with integrism and national Catholicism. Founded in Guadalajara, Jalisco, Mexico in the early 1930s, it traditionally operated a major degree of influence over the staff faculty and student youth of the Universidad Autónoma de Guadalajara. An outgrowth of the aftermath of the Cristero War and the disputes in Mexico over the introduction of Marxism into the state-ran education system, the organisation developed along staunch anti-communist lines, as well as positioning itself as opposed to what it claimed was a "Judeo-Masonic conspiracy."

The organisation grew further during the 1950s and played a leading role in the World Anti-Communist League, essentially leading the Latin America branch of the operation. Like the communists who they opposed, Los TECOS developed a number of front groups, with mass membership (not bound by the oaths of the secret society), which it sought to control and direct from behind the scenes. These groups were typically student, rightist Catholic and anti-communist groups, some engaged in violence with the far-left militants, while others were concerned with propaganda and more subtle lobbying.

Los TECOS spawned a number of branches in different states of Mexico. One of these, in Puebla, was known as El Yunque. This organisation, while sharing the same Catholic ultra-conservative worldview, split with Los TECOS in the early 1960s in a bitter feud over the religious question of the Second Vatican Council. Los TECOS and a number of their spiritual advisors, including the Jesuit priest, Fr. Joaquín Sáenz y Arriaga, were pioneers in forming the sedevacantism thesis, while El Yunque upheld the post-Concillar Vatican City-based claimants to the Papacy from Pope Paul VI onward as legitimate.

There are different opinions as to the origin of the name TECOS and its meaning. According to some sources, it is an acronym for Tarea Educativa y Cultural hacia el Orden y la Síntesis ('Educational and Cultural Work towards Order and Synthesis'). A second layer of meaning to the name is that teco (or in full tecolote) in Mexican Spanish signifies 'owl'; in a defence of the Universidad Autónoma de Guadalajara printed in The Washington Post, they claimed that the name was in reference to "the student's devotion to late night academic studies". A daughter of a Los TECOS member claimed "Yes, it does mean owl. Los Tecos are owls whose eyes are red. The members of the group are called Los Tecos because they are up all night doing their thing." Their influence at the university was such that, the association football team associated with it was named Tecos Fútbol Club.

The origins of Los TECOS finds its roots most directly in the conservative and Catholic pushback to political developments in Mexico in the 1920s, which came to the fore in the Mexican Revolution, in the aftermath of the fall of the moderate liberal-regime of the Porfiriato period. Although General Porfirio Díaz was a Freemason himself and adhered to Liberal Party positions, he did not actively enforce anticlericalism (even though this technically remained on the books), so as a compromise, his reign had been relatively tolerated by Mexican conservative elements. After radicals launched a coup known as the Plan of San Luis Potosí, which overthrew the moderate Díaz, some conservative opponents of the revolutionaries and politically active Catholics backed the rise of General Victoriano Huerta (who had been supported in this venture by the German Empire), but his reign was only short lived. In the aftermath of this, the Carrancistas and other radicals engaged in a general backlash against Mexican Catholics (whether or not they had backed Huerta) and developed anti-Catholic additions to the 1917 Mexican Constitution. At the same time, the Bolshevik October Revolution in Russia took place, which inculcated in Mexican conservative elements the idea that there was a global conspiracy to overthrow Christianity.

Against this "Masonic", secularist bourgeoisie vision of a society, Mexican Catholics founded a number of organisations to resist anticlericalism and coordinate together for the purpose of "Christian order in Mexico". This included the Asociación Católica de la Juventud Mexicana (ACJM), a mostly lay association sponsored by the Society of Jesus, which had been created in 1913 by Fr. Bernardo Bergöend, a French-born Jesuit, with the approval of José Mora y del Río, the Archbishop of Mexico. After the increasingly radical anticlerical additions to the Mexican Constitution of 1917 which enforced secular education as mandatory, saw the state take control of Church property and made it a requirements for priests to register with local government authorities to operate, a Catholic backlash grew, which was centered on the ACJM. They created a political party, the Partido Católico Nacional (PCN) which participated in the political process and in the 1920 election, backing the National Republicans, but lost out to the radically anticlerical Álvaro Obregón of the Partido Laborista Mexicano.

With the rise to power of Obregón's handpicked successor, Plutarco Elías Calles, also a Laborista, the so-called Calles Law in 1926 was enacted, which more closely enforced the 1917 Constitution and added in provisions of his own, such as seeking to exclude Catholic priests from participating in political life, a rebellion took place known as the Cristero War. As well as the ACJM which played a leading role on the Cristero side, the Liga Nacional Defensora de la Libertad Religiosa, which had been founded in 1925, would also play a central role. The Cristeros, though in many ways traditionalist, were not purely reactionary, endorsing a social Catholicism based on Rerum novarum, which saw them gain support from some of the peasantry and indigenous communities in their revolt against the liberal and radical "masonic" ruling-class. Ultimately, the institutional Church was persuaded to remove their support, as part of a United States-negotiated peace and militarily the rebellion drew to an end, though explicit violent state persecution continued until Calles was forced into exile by his successor, Lázaro Cárdenas, who had taken over the Partido Revolucionario Institucional (PRI) which Calles had founded.

During the years of the Maximato, when Calles continued to control affairs behind the scenes, the PRI began to take a more socialist direction; in 1931, Narciso Bassols, an atheistic materialist, became the first Marxist to hold office in Mexico as the Secretary of Public Education. With an anticlerical and anti-conservative speech entitled the Grito de Guadalajara, Calles openly announced a plan to enter a "psychological revolutionary period", where the state would take control of all education in Mexico to "seize the conscience of childhood" for the Revolution. After the rise of Cárdenas, Bassols continued on and developed the next phase of this revolutionary education program, known as "socialist education", whereby all schools would teach children according to the principles of Marxist materialism and atheism. In addition to this, Marxists had other roles in the Cárdenas regime: created from CROM, the labour union CTM was a major player at this time, under the control of Vicente Lombardo Toledano. Although never a member of the Mexican Communist Party, Lombardo Toledano was nevertheless, strongly pro-Soviet and his Jewish ancestry was used by elements of the ultra-right as evidence of the Cárdenas regime being a "Judeo-Masonic-Communist" conspiracy and the Bolshevisation of Mexico as taking place.