Guadalupe Ortiz de Landázuri (1916–1975) was a Spanish chemist, educator, and one of the pioneering women in Opus Dei. Born in Madrid on December 12, 1916, she was the only daughter among four children in a devout Catholic family. Despite the challenges of being one of only five women in her chemistry class at the Universidad Central de Madrid, she graduated in 1939, shortly after the Spanish Civil War. The war deeply affected her; her father, a military officer, was executed—an event that profoundly shaped her faith and resilience.

In 1944, Guadalupe met Saint Josemaría Escrivá, the founder of Opus Dei, and felt called to dedicate her life to God through her professional work. She joined Opus Dei, becoming one of its first female members. In 1950, she moved to Mexico to help establish Opus Dei's apostolic work among women. There, she initiated educational and social projects, including a student residence and a mobile medical clinic for underserved communities. Her efforts exemplified the Opus Dei ethos of finding holiness in ordinary life.

After returning to Spain due to health issues, Guadalupe continued her academic and apostolic work. She earned a doctorate in chemistry in 1965, receiving recognition for her research. Despite battling a serious heart condition, she remained active in teaching and mentoring. Guadalupe passed away on July 16, 1975, in Pamplona. Her beatification took place on May 18, 2019, in Madrid, making her the first laywoman of Opus Dei to be beatified.