Isumbras Took IV was the twenty-eighth Thain of the Shire.

One of the many children of Gerontius Took, Isumbras succeeded his older brother Isengrim Took III. He was ninety-two years old when he became a Thain and he ruled the Shire only for nine years. After his death, the title was inherited by his son, Fortinbras II Took.