The usual answer is Jeremiah
If someone asks for the Bible’s longest book, the usual answer is Jeremiah. In the King James Version, it contains slightly more words than Genesis, at roughly 33,000 words. Jeremiah opens by identifying the prophet and his calling in Judah, and its final chapter records events after Jerusalem’s fall (Jeremiah 1:1; Jeremiah 52:31).
That answer depends on how “longest” is measured. Word totals can shift between English translations because translators sometimes use more or fewer English words to express the same Hebrew or Greek text. Still, Jeremiah is the standard answer when people mean word count in the KJV.
The words of Jeremiah the son of Hilkiah, of the priests that were in Anathoth in the land of Benjamin:
Psalms is longest in other ways
Psalms may feel like the longest book because it contains 150 separate psalms, from its opening meditation on the righteous person to its final call for every living thing to praise the Lord (Psalms 1:1; Psalms 150:6). It also has more chapters and more verses than any other biblical book.
So both answers may appear in Bible quizzes or conversations. Jeremiah is longest by words in the KJV. Psalms is longest by chapters and verses. Knowing the measure being used clears up the apparent disagreement.
Let every thing that hath breath praise the Lord. Praise ye the Lord.
The longest chapter is Psalm 119
The longest individual chapter in the Bible is Psalm 119. It has 176 verses and is arranged around the Hebrew alphabet, with eight verses for each letter. Its first verse begins the meditation, and its final verse closes with a prayer from someone who knows they need God to seek them (Psalms 119:1; Psalms 119:176).
Psalm 119 repeatedly celebrates God’s law, commandments, statutes, and word. Here, “law” does not merely mean rules on a page. The psalmist treats God’s instruction as a guide for faithful life, especially when life is difficult.
Blessed are the undefiled in the way, who walk in the law of the Lord.
Why Jeremiah is worth reading
Jeremiah is not long simply because it contains many words. It follows a prophet who spoke to Judah through years of spiritual compromise, political fear, and eventual exile. God told Jeremiah to write down the words he had received, and Jeremiah dictated them to his scribe Baruch (Jeremiah 36:2; Jeremiah 36:4).
It can be a demanding book, but it carries both warning and hope. Amid the grief over Jerusalem’s ruin, God promises that he has not abandoned his people and speaks of a future covenant written on their hearts (Jeremiah 31:33). If you begin reading it, take it slowly. Its length gives space for an honest, searching conversation between God and a people who have wandered.