Oona Castilla Chaplin (born 4 June 1986) is a Spanish–Swiss actress. Her roles include Talisa Maegyr in the HBO TV series Game of Thrones, Kitty Trevelyan in the BBC drama The Crimson Field, and Zilpha Geary in the series Taboo.

A member of the Chaplin family, she is the daughter of actress Geraldine Chaplin, granddaughter of English filmmaker and actor Charlie Chaplin, and great-granddaughter of Irish-American playwright Eugene O'Neill. She was named after her maternal grandmother Oona O'Neill, Charlie Chaplin’s fourth and final wife.

Oona Castilla Chaplin, ou simplesmente Oona Chaplin, é uma atriz, bailarina e dançarina espanhola, neta do ator britânico Charlie Chaplin e bisneta do dramaturgo norte-americano Eugene O'Neill.