Why is the wedding ring worn on the fourth finger of the left hand?

Here is the version you have heard: the ancient Egyptians believed a vein ran straight from the fourth finger of the left hand to the heart, so that is where the ring went, and it has gone there ever since. Every jeweler tells it. It is a lovely story, and it is wrong in nearly every particular, starting with the vein.

What the oldest text actually says

The earliest surviving mention comes from a Roman scholar named Aulus Gellius, writing his Attic Nights around AD 170. He is not reporting an Egyptian belief. He is reporting what a Greek writer named Apion claimed Egyptian anatomists had found: "upon cutting into and opening human bodies," Apion said, "a very fine nerve proceeded from that finger alone, and made its way to the human heart."¹ A nerve. Not a vein. And Gellius adds the detail everyone skips: the Greeks wore the ring there too, and "the Roman men commonly wore their rings in that way."¹

Two centuries later Macrobius repeated the claim at a fictional dinner party in his Saturnalia, with a physician explaining that a certain nerve born in the heart runs forward to the finger next to the little one on the left hand.² Still a nerve.

Where the vein came from

The vein is a seventh-century edit. Isidore of Seville, compiling his Etymologies, wrote that people first began wearing rings on the fourth finger "because a certain vein reaches from there to the heart."³ Nerve became vein, and the vein stuck. By the twelfth century it was in canon law: the Decretum Gratiani says the ring belongs on the fourth finger because of a vein "which, it is said, carries blood to the heart."⁴

The Latin name you see on every wedding blog, vena amoris, the vein of love, is younger still. Its first known appearance in English is in a law book called A Treatise of Spousals, written by the church lawyer Henry Swinburne, who died in 1624. The manuscript sat in the library of Lincoln's Inn until someone found it and printed it in 1686.⁵ So the phrase that sounds like ancient Rome was published in London the year before Newton's Principia.

Why it is the left hand, in English

For English-speaking couples the finger was settled by a prayer book. Thomas Cranmer's Book of Common Prayer of 1549 has the priest hand the ring to the groom "to put it upon the fourth finger of the woman's left hande," followed by the words that are still in the service: "With this ring I thee wed."⁶ Four and a half centuries of English weddings have followed that rubric.

Much of the world did not. Orthodox Christians wear the wedding ring on the right hand, and one Orthodox Church in America priest, asked which hand is correct, answered that the left-hand custom is "a peculiarly American custom."⁷ In Germany and Austria the engagement ring goes on the left and the wedding ring moves to the right at the ceremony, a practice shared across Poland, Russia and much of eastern Europe.⁸ Norway, Denmark, Greece and Spain are right-hand countries too.⁹

The anatomy

There is no vena amoris. The veins in your hand drain the fingers more or less identically, and none of them has a private line to the heart.¹⁰ Every finger you own is connected to your heart, which is a nicer thought anyway. The claim would have needed William Harvey's seventeenth-century work on circulation to be tested, and by then the finger was already fixed by custom and canon law.¹¹

Why your mother cares

The finger is one of the oldest continuous habits in the whole ceremony. Your grandmother put the ring where her grandmother did, and the rule was already four hundred years old in English when either of them married. Nobody in your family invented it, nobody sold it to them, and nobody profits from it. That is rare on these shelves.