What is the name of the character played by Lily James?

The character played by Lily James in Downton Abbey is Lady Rose MacClare. She is introduced as the youngest child of Hugh and Susan MacClare, the Marquess and Marchioness of Flintshire, and a cousin of the Crawley family.

Rose joins the story during the third series after her parents go to India. She stays with the Crawleys while family tensions and her mother's disapproval of her lively, independent behaviour shape her storyline. Unlike the more reserved Crawley sisters, Rose is sociable, modern-minded and comfortable in London’s changing post-war world.

She later becomes engaged to Atticus Aldridge, and after their marriage her formal name is Lady Rose Aldridge, née MacClare. That later surname is the main possible source of confusion, but the character is introduced and commonly identified as Lady Rose MacClare. Lily James played Rose from 2012 through the television series finale, though she did not appear in the subsequent films.