Megan McDonnell is an American screenwriter best known for her work on Marvel Cinematic Universe projects WandaVision (2021) and The Marvels (2023).

McDonnell attended Harvard University as an undergraduate, where she was a member of the Hasty Pudding Club.

She graduated from the Peter Stark Producing Program at USC with an MFA in 2016.

McDonnell began her career as the co-director and executive producer on the 2016 short film Meet Cute. She then rose to prominence after writing two episodes of the Disney+ series WandaVision, set in the Marvel Cinematic Universe (MCU). In January 2020, she entered negotiations to write the screenplay for the 2023 MCU film The Marvels, and she eventually co-wrote the film with Nia DaCosta and Elissa Karasik. In August 2022, she wrote episodes for the Marvel Studios series Agatha All Along.