The two were in their car heading to Linate Airport when paparazzi snapped them kissing, reported AceShowbiz.
Stewart and Maxwell, both 26, were on a romantic getaway in Milan.
The "Twilight" star was wearing a bomber jacket with metallic zipper and sunglasses, while Maxwell wore a burgundy leather motorcycle jacket and light wash black skinny jeans.
Stewart and Maxwell have been romantically linked since last May, when they were spotted leaving the Met Ball together.
Prior to Maxwell, the actress allegedly dated several girls, including her assistant Alicia Cargile, rock band PVRIS' member Lyn Gunn and French singer Soko.
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