Which prophet's book is the shortest in the Hebrew Bible?

Obadiah's book is the shortest book in the Hebrew Bible.

The Book of Obadiah contains a single chapter and 21 verses. In the Hebrew text it has about 440 words, making it shorter than the other books of the Tanakh. Its compact size does not mean its subject is minor: the prophecy announces judgment against Edom, a neighboring people traditionally descended from Esau, and promises restoration for Israel.

Obadiah's central accusation is that Edom took advantage of Jerusalem's catastrophe, participating in or benefiting from violence against Judah. The book's famous “day of the Lord” theme presents divine judgment as extending beyond one nation and ultimately affecting all peoples.

Readers sometimes confuse “shortest book in the Hebrew Bible” with “shortest biblical book” in every tradition. Obadiah is the shortest book of the Tanakh, but several New Testament letters are shorter by word count in Greek, including 3 John, 2 John, and Philemon. The answer also refers to the book attributed to the prophet Obadiah, not to the length of a biography about him; very little biographical information about the prophet survives.