Molly Helen Shannon (born September 16 1964) is an Emmy-nominated American actress and writer.

Before "Saturday Night Live" (1975), Molly Shannon had a struggling career in films. She gained notice as Meg in the present day sequences in the horror film remake of Phantom of the Opera, The (1989) with Robert Englund and Jill Schoelen, which was a major hit in 1989. Her big break came in 1995 when she joined the cast of "Saturday Night Live" (1975), where she played various characters, the best known of which was Mary Katharine Gallagher. After her departure from SNL she refocused on a film career. She again played Mary Katharine Gallagher in Superstar (1999) and had a supporting role in Never Been Kissed (1999). Her more recent films include How the Grinch Stole Christmas (2000), Shallow Hal (2001), Santa Clause 2, The (2002), Serendipity (2001) and Osmosis Jones (2001).