Calixto O. Zaldivar (September 13, 1904 - October 13, 1979) was born in Pandan, Antique, Philippines. He graduated in law from the University of the Philippines and a third placer in the Bar Exam. He uniquely held positions in all branches of the government. In Legislative he served as a Representative of Antique from 1934–1935; in the Executive branch, as Governor of Antique, 1951–1955 and Executive Secretary of the President of the Philippines; and in judiciary, as Associate Justice of the Supreme Court from 1964-1974.
He distinguished himself by writing some of the “most timeless opinions and equally the most penetrating dissents in the history of the Bill of Rights” during the tumultuous decade in the Philippine History.
He acquired the reputation of being an independent-minded member of the court especially during the deliberations on the issues arising out of the declaration of the Martial Law and the validity of the 1973 Constitution. When many bent to the rule of the dictator, Zaldivar was never cowed but continued to dissent when he should. He was a defender of civil and political liberties, who also promoted social sciences in addition to his work in religion (being a stalwart Aglipayan), law, government and statesmanship areas which his children are now heavily involved.
- Spouse: Elena Ang
- Children: Lorna, Nona, Enrique, Salvacion and Calixto, Jr.
- Religion: Iglesia Filipina Independiente (also Aglipayan Church)