Critical scholars say the book of Jonah is fiction. 

“A light satire, with no prentions to being historical . . . This fictional form is unique in the prophetic tradition”—Catholic commentary on Jonah

“There are convincing reasons why the book cannot be historical”—Dictionary of the Bible, by John L McKenzie

“Jesus replied, ‘Only an evil, adulterous generation would demand a miraculous sign; but the only sign I will give them is the sign of the prophet Jonah. For as Jonah was in the belly of the great fish for three days and three nights, so will the Son of Man be in the heart of the earth for three days and three nights. The people of Nineveh will stand up against this generation on judgment day and condemn it, for they repented of their sins at the preaching of Jonah. Now someone greater than Jonah is here–but you refuse to repent'”—Matthew 12:39-41 NLT (also, see Matthew 16:4 and Luke 11:29,30,32). Jesus Christ, the Son of God, regarded the book of Jonah as historical, and beneficial. So did Bible writers Matthew and Luke.

Many Protestant and Catholic scholars and commentaries regard the book of Jonah as fiction, as noted above. We can see a sharp contrast in the way that Jesus Christ viewed the book of Jonah — as entirely historical —  with the way that modern some “scholars” view it. So, why is the book of Jonah viewed as fictional? What do the critics say?

— The famous account of Jonah being swallowed by the huge fish, and kept alive inside it for three days, seems unrealistic, incredible, and far-fetched (1:17; 2:10). Whales don’t live in the eastern Mediterranean, and no sea creature could swallow a man whole, much less hold him alive in its “belly” for three days. 

— The sudden “violent storm” (1:4) and its sudden end (1:15), and the sudden, rapid rate of growth of the “leafy plant” and its demise quick demise “the next morning at dawn” by a “worm” (4:6,7), seem fantastically unreal.

— The author of Jonah seems to have adopted the Jonah of 2 Kings 14:25 as its hero, and the name seems to have been chosen at random.

— Jonah 3:9 is similar to Joel 2:14, suggesting that Jonah was a late work, written long after the lifetime of the historical prophet. Many claim it is a post-exilic work because of the doctrine of the book, and the numerous Aramaisms and features of the later Hebrew prose style and grammar.

— Jonah’s psalm prayer  (2:1-9) makes no sense in context, because Jonah is depicted as praising God for saving him while he’s still inside the huge fish.

— The account seems to lack accurate knowledge of geography of ancient Nineveh, for example, by asserting that, “Nineveh was an exceedingly great city beyond compare, a three days’ walk” (3:3 NASB). Archaeological evidence has revealed that the circumference of the walls surrounding ancient Nineveh was only about eight miles (13 kilometers). The statement, “Nineveh was,” indicates Nineveh was no longer in existence at the time of the book’s writing.

— The book is not historical because the Bible does not give the name of the “king of Nineveh,” nor does the title “king of Nineveh” (3:6)  appear in any Assyrian records, and the exact spot where Jonah was spewed out is not named.

— The king’s decree that even animals should participate in the repentance seems fantastic (3:7,8).

— There is no extant Assyrian historical record that a prophet named Jonah visited Nineveh, or that Nineveh ever experienced a mass revival or conversion (3:6-10), which seems to be wildly fictional in any case. 

— The book is not written in first person, but in third person, which means it cannot have been written by Jonah.

All of these objections to the historicity of Joel are refuted by the evidence:

— Most of the objections to the authenticity of Jonah spring from the critics denial of God’s sovereignty over the natural world and history, including his ability to intervene supernaturally in the created order. In the book, “Yahweh” is presented as Creator, “the God of Heaven, who made both sea and dry land” (1:9 NJB). Creation responds obediently to his every command (1:4,15,17; 2:10; 4:6-8), serving the will of the Creator. If God can create the universe (Genesis 1:1), then he owns it and has control over it.

— The account of Jonah being swallowed by the huge fish is miraculous only in the sense that God caused it to swallow Jonah shortly after he was thrown into the sea. There is evidence that the ancient seaport at Joppa was a headquarters for whalers. It is not stated exactly what kind of “huge fish” (1:17) swallowed Jonah. It could have been one that is now extinct. The sperm whale, for example, has a huge head that is about one-third of the length of its body, and is very capable of swallowing a man whole. There have, in fact, been a few documented reports of men being swallowed by huge fish, and coming out alive. While most translations use the word “belly” to describe where Jonah was “inside the fish,” (1:17 NLT), the Hebrew is not that precise. He could have been in the oral cavity of a large-mouthed whale. Since whales are warm-blooded air breathers that periodically surface for air, it therefore could have provided Jonah with the oxygen he needed, while its body heat would have prevented Jonah from being overcome with hypothermia.

— The similar wording of Jonah 3:9 and Joel 2:14 do not prove that they were written about the same time, and certainly not post-exilic.

— The usual practice of ancient kingdoms was to document their successes, even with some embellishment, while minimizing or even omitting  embarrassing or unflattering things, so the lack of external documentation of Jonah’s visit to Nineveh, and the Ninevites repentance, is not surprising.

• The book’s statement that “to cross it took three days” (3:3) may include its suburbs, and may mean going around its circumference. In both Biblical and modern usage, the name of a city may include its suburbs. Genesis 10:11,12 refers to Nineveh, Rehoboth Ir, Caleh and Resen combined as being “the great city” (NASB), and this area had a circumference of about 60 miles (97 kilometers), which would be “a three days’ walk.” This region around Nineveh includes modern Kyunjik, Khorsabad, and Nimrod. The past tense, “Nineveh was” (3:3), does not preclude an 8th century date of writing, and may simply indicate the status of the city when the prophet arrived.
• Bible writers often referred to themselves in the third person (Exodus 24:1-18; Isaiah 7:3; 20:2; 27:2,5,6,21; Jeremiah 20:1,2; 26:7,8,12; 37:2-6,12-21; Daniel 1:6-13; Amos 7:12-14; Haggai 1:1,3,12,13; 2:1,10-14,20; John 21:2). Some secular historians, such as Xenophon and Thucydides, also did this, but the authenticity of their accounts is never called into question.
• The book’s candor regarding Jonah and his bad attitude toward his commission from God to preach destruction to the Ninevites, and also about God’s mercy toward them after their repentance, is outstanding. Fictional accounts do not usually reveal such candor.
• The Ninevites’ repentance at Jonah’s preaching was likely a short-lived event, and doesn’t mean they became true worshippers of Yahweh. Besides, Assyrian history back then was written by worshippers of pagan gods, who may have viewed such actions of the Ninevites as unflattering to their gods, and therefore omitted it.
• The lack of certain details does not prove the book is not historical, because all historical narratives are condensed accounts. Historians only record the information they think is necessary to accomplish their purpose. “There is not a single one of the ancient historians in whose works such completeness can be found; and still less do the biblical historians aim at communicating such things as have no close connection  with the main object of their narrative, or with the significance of the facts themselves”—Biblical Commentary on the Old Testament, The Twelve Minor Prophets, Vol I, page 381, by C F Keil
• With the book’s opening statement, “The word of Yahweh was addressed to Jonah” (1:1), the book claims to be from Almighty God. The Jews since the time of Jonah (8th century BCE) have viewed the book of Jonah as being one of “the Prophets” (Matthew 5:17; Luke 16:16,31; 24:27,44) inspired by God and part of their Scriptural canon. “It is in fact inconceivable . . . that the Jews would have received such a book into the canon of Scripture without the most conclusive evidence of its genuineness and authenticity”—The Imperial Bible Dictionary, Vol 1, page 945
• The strongest proof of all, of course, is that of Jesus Christ, the Son of God, who authoritatively expressed his view that the book of Jonah is entirely historical (Matthew 12:39-41; 16:4; Luke 11:29,30,31). If the book Jonah is fictional, then Jesus was preaching fiction, and Matthew and Luke’s gospels contain fiction, or, even worse, Jesus himself may be a fictional character.