Bishop Oscar Cantú S.T.L. was born December 5, 1966, in Houston, Texas, the son of Ramiro and Maria de Jesus Cantú, natives of small towns near Monterrey, Mexico. He is the fifth of eight children, five boys and three girls. Pope Benedict XVI, through the Vatican’s Congregation of Bishops, named Auxiliary Bishop Oscar Cantú as the Apostolic Administrator for the Archdiocese of San Antonio effective May 26, 2010 as Archbishop José Gomez vacated his seat as Archbishop of San Antonio and assumesd his position as coadjutor archbishop of the Archdiocese of Los Angeles, CA.

Bishop Cantú is a product of Houston's Catholic schools, attending Holy Name Catholic School and St. Thomas High School. He earned his Bachelor of Arts degree from the University of Dallas. He then received his Master in Divinity and Master in Theological Studies from the University of St. Thomas in Houston. He continued at the Pontifical Gregorian University, located in Rome, where he earned his S.T.L. in Dogmatic Theology. He currently is completing his work for a doctorate in Dogmatic Theology. Bishop Cantú was ordained a priest of the Diocese of Houston on May 21, 1994.

He has spent his priestly career working in parishes throughout the Houston metropolitan area. His first assignment following his ordination was as parochial vicar at St. Christopher Parish in Houston. Since 2003, he has taught at the University of St. Thomas in Houston. He also has taught at the University of St. Thomas School of Theology located at St. Mary's Seminary. Bishop Cantú is fluent in Spanish, Italian, and French.

While still a seminarian, Bishop Cantú worked on a committee consisting of diocesan leaders and chaired by Laredo's Bishop James Tamayo. Its purpose was to develop, promulgate, and promote a plan for Hispanic ministry. Since his priestly ordination, Bishop Cantú has participated in number of ministries and movements in Houston. He was involved in the Movimiento Familiar Cristiano (MFC), a national network of parish/neighborhood small groups of Catholics and their families who come together to reinforce their Christian values. He conducted three retreats per year with the youth of the MFC in the Galveston-Houston Archdiocese. Bishop Cantú also worked with those preparing for marriage through the Engaged Encounter ministry. From 2004 to 2007, Bishopú co-hosted an interfaith radio show in Houston called "Show of Faith." His co-hosts included a Jewish rabbi and a Protestant minister. The program discussed issues from the perspective of their individual faith traditions.

Bishop Cantú has also been involved in The Metropolitan Organization (TMO). Its mission is to publicly address important social issues in the community such as fair housing, immigration, education and many others. Bishop Cantu was appointed Titular Bishop of Dardano and Auxiliary Bishop of San Antonio on April 10, 2008.

Bishop Cantú was ordained auxiliary bishop of the Archdiocese of San Antonio on June 2, 2008 at St. Mark the Evangelist Church, San Antonio by Archbishop Gomez. He has overseen the Office of Catholic Schools and the Office of Youth Ministry, and The Office of Education and Adult Formation, while working closely with pastors and parishes in a variety of roles, and assisting Archbishop Gomez in carrying out his many official and pastoral duties. He also served as pastor of Holy Trinity Parish in San Antonio.