Katherine Parkinson (born March 9, 1978) is an English actress. She appeared in the Channel 4 comedy series The IT Crowd as Jen Barber, for which she received a British Comedy Best TV Actress Award in 2009 and 2014, and was nominated twice for the BAFTA Television Award for Best Female Comedy Performance, winning in 2014.

Parkinson studied at the London Academy of Music and Dramatic Art, and has appeared on stage in the plays The Seagull (2007), Cock (2009), and Home, I'm Darling (2018), for which she was nominated for the Olivier Award for Best Actress in a Play. Parkinson was also a main cast member of the series Doc Martin for three series (2005–2009). She co-starred in all three series of Humans, a science-fiction drama on AMC/Channel 4, which aired from 2015 until 2018. She has also appeared in the films The Boat That Rocked (2009) and The Guernsey Literary and Potato Peel Pie Society (2018).