The Old Testament prophet painted above the Sistine Chapel altar is Jonah.
Michelangelo placed Jonah at the eastern end of the ceiling, directly above the High Altar. The prophet is identifiable through the large fish behind him, recalling the biblical story in which Jonah is swallowed and later restored after three days. His prominent position was not accidental: Christian interpreters connected Jonah's ordeal with Christ's death and resurrection.
Jonah is one of seven male prophets on the ceiling. The other prophetic figures include Jeremiah, Ezekiel, Joel, Isaiah, Daniel, and Zechariah; five female Sibyls appear alongside them. Each figure contributes to the ceiling's larger theme of prophecy and the promise of salvation.
A frequent source of confusion is the distinction between the ceiling and the altar wall. Jonah is on the ceiling above the altar, while Michelangelo's later The Last Judgment occupies the wall behind it. Daniel, Isaiah, and Jeremiah are also present elsewhere in the ceiling program, but none occupies Jonah's altar-side position.