Who wrote the Psalms? Many people, over roughly a thousand years. David’s name sits on more of them than anyone else’s, but he did not write the whole book, and close to a third of the 150 psalms name no author at all.
Who the titles actually name
Most psalms carry a short heading above the first line. These headings were added early, though not necessarily by the same hand that wrote the poem below them, and they name several different people. Seventy-three psalms carry David’s name. Asaph gets credit for twelve, the sons of Korah for eleven, Solomon for two, and Heman and Ethan one each. Psalm 90 carries Moses’ name, which would make it the oldest psalm in the book by centuries. That leaves roughly fifty psalms with no name attached, a third of the collection, written by people history never recorded.
What “of David” is actually claiming
Even the psalms with David’s name attached carry a real question. The Hebrew phrase behind the heading, le-David, uses a preposition that can mean several things: written by David, written for David, written about David, or written in David’s style by someone else entirely. Ancient Hebrew did not always distinguish these the way English does, and scholars have argued the point for a long time without settling it. Some of the seventy-three read like they came from a king’s own hand, wrestling with guilt or fear or triumph in the first person. Others read more like later poets writing in a voice they associated with him, the way a modern hymn might be composed “in the style of” an older tradition. Both readings stay on the table. Neither one has won.
A hymnbook assembled over centuries
The clearest evidence that the Psalms were not written by one person, or even in one era, sits right in the text. Psalm 137 opens “by the rivers of Babylon, there we sat down and wept, when we remembered Zion.” That is a psalm written by people already in exile, mourning a fallen Jerusalem, which puts it centuries after David died as king in a Jerusalem that still stood. A psalm like that could not have come from David’s pen no matter what a heading says. The most reasonable picture, and the one most scholars hold, is that the Psalms grew as a collection over thirty generations or more: older poems from the time of the monarchy, temple songs added as worship developed, and psalms written during and after the Babylonian exile, all gathered, arranged, and given their final shape sometime after the exiles returned home. Genesis has its own version of this same puzzle about single authorship, which we get into in who wrote Genesis.
Five books, one collection
The finished Psalter is not one long list. It is divided into five books: Psalms 1 to 41, 42 to 72, 73 to 89, 90 to 106, and 107 to 150. Each of the first four books closes with a short burst of praise, a doxology, often ending in a doubled “Amen and Amen.” Psalm 150, the last psalm in the book, is one long doxology by itself, closing out the fifth book and the whole collection at once. Some scholars think the five-book division was meant to echo the five books of the Torah. Others see it as a simpler byproduct of how earlier, smaller collections got stitched together over time. Either way, by the time the book reached its final form, someone was thinking carefully about how the whole thing should end: not with a complaint or a question, but with praise.
Why the number of authors changes nothing about how it gets used
None of this is a problem to explain away. A hymnbook built by many hands over many centuries, with some of those hands never named, is still exactly what a hymnbook is supposed to be: words that outlasted the person who first said them, because someone else needed them too. A shepherd-king’s fear in Psalm 23 and an anonymous exile’s grief in Psalm 137 sit twenty feet apart on the same page, and both have been prayed by people who had never met either author and never needed to. That is not a weakness in the text. For more on how the whole Bible was assembled this way, across many writers and a long stretch of time, see who wrote the Bible and when it was written. The Psalms have been prayed for close to three thousand years by people who mostly never asked who wrote the line they were saying. Knowing the answer is more complicated than one king does not change that. It just tells you what kind of book you are actually holding.