Karen Trust Grassle (born February 25, 1942) is an American actress, known for her role as Caroline Ingalls in the NBC television drama series Little House on the Prairie.

After summers at the Stanford Contemporary Workshop playing leads and two summers at the Colorado Shakespeare Festival playing classical roles, her first professional engagement was a season at the Front Street Theatre, Memphis, TN. upon return from London. While living in New York City, she worked at resident and stock theatres throughout the country, also appearing on PBS in original works and on networks in three soap operas. She made her Broadway debut in the short-lived 1968 play The Gingham Dog. Grassle played in Butterflies Are Free on Broadway (as stand-by with Gloria Swanson, Rosemary Murphy, etc.) as well as at the Elitch Theatre in Denver, Colorado, in June 1972, along with Maureen O'Sullivan and Brandon deWilde, who was killed before leaving town after the performances ended. Grassle starred in the Shakespeare in the Park "Cymbeline." with Christopher Walken, Sam Waterston, and Bill Devane.