Gustavo Díaz Ordaz Bolaños (Spanish pronunciation: [ɡusˈtaβo ˈði.as oɾˈðas]; 12 March 1911 – 15 July 1979) was a Mexican politician and member of the Institutional Revolutionary Party (PRI). He served as the President of Mexico from 1964 to 1970. Previously, he served as a member of the Chamber of Deputies for Puebla's 1st district, a senator of the Congress of the Union for Puebla, and Secretary of the Interior.

Díaz Ordaz was born in San Andrés Chalchicomula, and obtained a law degree from the University of Puebla in 1937 where he later became its vice-rector. He represented Puebla's 1st district in the Chamber of Deputies from 1943 to 1946. Subsequently, he represented the same state in the Chamber of Senators from 1946 to 1952 becoming closely acquainted with then-senator Adolfo López Mateos. Díaz Ordaz was a CIA asset, known by the cryptonym, LITEMPO-2.

Díaz Ordaz joined the campaign of Adolfo Ruiz Cortines for the 1952 election and subsequently worked for the Secretariat of the Interior under Ángel Carvajal Bernal. He became the secretary following López Mateos' victory in the 1958 election, and exercised de facto executive power during the absences of the president, particularly during the Cuban Missile Crisis. In 1963, the PRI announced him as the presidential candidate for the 1964 election, he received 88.81% of the popular vote.

His administration is mostly remembered for the student protests that took place in 1968, and their subsequent repression by the Army and State forces during the Tlatelolco massacre, in which hundreds of unarmed protesters were killed. His presidency also took place during a period of high economic growth known as the Mexican Miracle, as well as hosting both the 1968 Summer Olympics and 1970 FIFA World Cup, the first country to have organized both showpiece events two years apart.

After passing on the presidency to his own Secretary of the Interior Luis Echeverría, Díaz Ordaz retired from public life. He was briefly the Ambassador to Spain in 1977, a position he resigned from after strong protests and criticism by the media. He died of colorectal cancer on 15 July 1979 at the age of 68.

Despite high economic growth during his presidency, Díaz Ordaz is considered one of the most unpopular and controversial modern Mexican presidents, largely for the Tlatelolco massacre and other repressive acts, which would continue into the presidencies of his successors.

Gustavo Díaz Ordaz Bolaños was born on 12 March 1911 in San Andrés Chalchicomula (now Ciudad Serdán), Puebla. His family was of mixed Spanish and Indigenous ancestry. He had two older siblings, Ramón (born 1905) and María (born 1908), and two younger siblings, Ernesto and Guadalupe. In his later years his father, Ramón Díaz Ordaz Redonet, worked as an accountant. However, for a decade he served in the political machine of President Porfirio Díaz, becoming the jefe político and police administrator of San Andrés Chilchicomula. When Díaz was ousted by revolutionary forces in May 1911 at the outbreak of the Mexican Revolution, he lost his bureaucratic post in the regime change. Subsequently, the family's financial situation was insecure, and Díaz Ordaz's father took a number of jobs and the family frequently moved. He claimed ancestry with conqueror-chronicler Bernal Díaz del Castillo. Gustavo's mother, Sabina Bolaños Cacho de Díaz Ordaz, was a school teacher, described as "stern and pious". Gustavo, as well as his elder brother Rámon, had a weak chin and large protruding teeth and was skinny. "His mother would freely say to anyone, 'But what an ugly son I have!'" His lack of good looks became a way to mock him when he became president of Mexico.

The comedian Chespirito (real name Roberto Gómez Bolaños) was his first cousin once removed.