Late goals by Juan Zuniga and Troy Deeney helped Watford achieve their first victory over Manchester United in 30 years.
The Hornets took the lead on 34 minutes after Daryl Janmaat cut the ball back for Etienne Capoue to score his fourth goal of the season.
United were level on 62 minutes when Valon Behrami could only deflect Zlatan Ibrahimovic's cross into Marcus Rashford’s path and the 18-year-old netted from close range.
Watford restored their lead when Roberto Pereyra cut the ball back to the substitute to score with his first touch.
Deeney made it 3-1 with a penalty after Zuniga had been fouled by Marouane Fellaini.
Man of the Match: Sebastian Prodl
See: Watford report | Man Utd report
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