Cniva (Kniwa, meaning "knife") (flourished mid-3rd century CE) is the Gothic chieftain who invades the Roman Empire in the third century CE.

He successfully conquers the city of Philippopolis, now present day Bulgarian city Plovdiv, and kills the emperor Decius and his son Herennius Etruscus at the Battle of Abrittus as he is attempting to leave the Roman Empire.

He is allowed to leave with his spoils and is paid tribute to stay out of the empire.