- The eldest daughter of Meryl Streep.
- Named after her maternal great-grandmother; has been called Mamie since she was an infant.
- As a toddler, made her movie debut in the 1986 comedy-drama Heartburn.
- Cast in the 2005 off-Broadway production of Mr. Marmalade; received a Theatre World Award for her performance.
- Made her small-screen debut in the 2008 HBO series John Adams.
- In 2008, won the role of Cécile Volanges in the stage adaptation of Les Liaisons Dangereuses; it marked her Broadway debut.
- Spokesmodel for fashion designer Gerard Darel's 2009-10 collection.
- Benjamin Walker — Husband (separated)
- Grace Gummer — Sister
- Donald J. Gummer — Father
- Meryl Streep — Mother
- Louisa Jacobson Gummer — Sister
- Mary Streep — Grandmother
- Henry Gummer — Brother
- Northwestern University, Evanston, Illinois, United States (BA in Theatre, 2005); attended the British American Drama Academy, London, England