Louise Whitfield Carnegie (March 7, 1857 – June 24, 1946) was the wife of philanthropist Andrew Carnegie.

Daughter of New York City merchant John D. Whitfield, Louise was born in the Gramercy Park neighborhood of Manhattan. On April 22, 1887 she married Carnegie at her family's home in New York City in a private ceremony officiated by a pastor from the Church of the Divine Paternity, a Universalist church to which the Whitfields belonged. At the time of the marriage, Louise was 30; Carnegie was 51. As wedding gifts from her husband, Louise received an approximate annual income of $20,000 and a home (formerly owned by Collis Potter Huntington) at 5 West 51st Street.

Louise gave birth to the couple's only child Margaret in 1897. Louise and her daughter were members of the Brick Presbyterian Church (New York City).

After Carnegie's death Louise continued making charitable contributions to organizations including American Red Cross, the Y.W.C.A., the Cathedral of St. John the Divine, numerous World War II relief funds, and $100,000 to theUnion Theological Seminary. She spent her summers at Skibo Castle.

In 1934 she was honored with the Gold Medal of the Pennsylvania Society.

She died at the age of 89 and was buried in Sleepy Hollow Cemetery, in Sleepy Hollow, New York.