Fiona Frost (フィオナ・フロスト, Fiona Furosuto) is one of the recurring characters of the SPY x FAMILY series. She is a spy for WISE who acts under the codename "Nightfall" (〈夜帷とばり〉, Tobari). She works undercover as an office worker at Berlint General Hospital to support Loid Forger's cover story.
