Grimoald I (or Grimvald) (c. 610 – 671) is duke of Benevento (651–662) and king of the Lombards (662–671).

Born probably before 610 to Duke Gisulf II of Friuli and the Bavarian princess Ramhilde, daughter of Duke Garibald I of Bavaria, he succeeds his brother Radoald (646–651) as duke of Benevento.

Before this, he is, along with Radoald, a regent for their mentally incapable adoptive brother Aiulf I from 642 to Radoald's succession.

He marries the princess Theodota, daughter of King Aripert I.

Their son is Garibald.