Martha Maria Yeardley Smith (/ˈjɑːrdli/ YARD-lee; born July 3, 1964) is an American actress. She voices Lisa Simpson on the animated television series "The Simpsons."

Smith began acting in 1982 after graduating from drama school. In 1984 she moved to New York, where she appeared in a Broadway production of Tom Stoppard's play "The Real Thing." Her film debut came in 1985 in "Heaven Help Us," followed by roles in "The Legend of Billie Jean" and "Maximum Overdrive." In 1986 she moved to Los Angeles and got a recurring role on the television series "Brothers."

In 1987 Smith auditioned for the "Simpsons" shorts on "The Tracey Ullman Show." Smith intended to audition for the role of Bart Simpson, but the casting director considered her voice too high, and she was cast as Bart's sister Lisa. In 1989 the shorts were spun off into their own half-hour show, "The Simpsons." For her work on "The Simpsons," Smith won a Primetime Emmy Award for Outstanding Voice-Over Performance in 1992.

In addition to "The Simpsons," Smith appeared in the sitcom "Herman's Head" as Louise, and also appeared in recurring roles as Marlene on "Dharma & Greg" and Penny in two episodes of "Dead Like Me." She has appeared in several films, including "City Slickers," "Just Write," "Toys," and "As Good as It Gets." In 2004 Smith performed an off-Broadway one-woman show, "More," at the Union Square Theatre in New York. In addition to "The Simpsons," Smith has recorded several voice-overs, only for commercials and the film "We're Back! A Dinosaur's Story." Smith starred in and executive produced the independent romantic comedy "Waiting for Ophelia," which had its world premiere at the Phoenix Film Festival in April 2009.