The pairing is popular for the wrong reason and defensible for a better one. People put Aphrodite and Freyja together because both are "the love goddess", which is a job title invented by later handbooks. What actually makes the comparison worth an hour is that both are far more dangerous than their reputations, both have documented links to the dead, and both were domesticated by the same modern process of turning complicated goddesses into a single attribute.
Start with what neither of them is
Neither is a goddess of romance. Aphrodite's domain is eros as a compelling force — something that happens to you, often against your judgement, with consequences. The most-quoted ancient hymn to her describes her overpowering gods, animals and men alike, and the epic in which she is most prominent turns on her having caused a war by paying a bribe. Freyja's associations are with desire, gold, war-dead and a specific kind of magic, in a body of verse that also has other gods openly accuse her of sleeping with everyone in the hall. Both goddesses are treated by their own traditions as a problem as much as a pleasure.
What they genuinely share
Half the slain. This is the fact that makes the comparison serious. The eddic verse states plainly that Freyja receives half of those who fall in battle at her hall and dwelling, and Odin the other half — and she chooses first. A goddess associated with love who has an equal claim with the chief god on the war-dead is not a footnote; it is a structural fact about Norse religion that most retellings simply omit.
Armed worship. Aphrodite was worshipped armed in more than one place, notably at Sparta, where Pausanias reports an armed cult image, and at Cythera. Whether that reflects an old Near Eastern inheritance or a local Spartan idiom is argued, but the images existed and were not a joke.
Near Eastern shadow. The strongest scholarly case for Aphrodite's background — argued by Walter Burkert and Martin West among others — connects her to Levantine Astarte and ultimately to Mesopotamian Inanna, by way of Cyprus, where her oldest major sanctuary stood at Paphos. Inanna is unambiguously a goddess of both sexual desire and war. If that derivation holds, Aphrodite's martial aspect is not an oddity but a residue.
Magic that is not respectable. Freyja is credited with bringing seiðr to the Æsir, a form of magic whose practice by a man carried a serious social stigma. Aphrodite's equivalent is the girdle — the embroidered band that compels desire, which she lends to Hera to deceive Zeus. Both goddesses control a technique that overrides another's will.
Where the comparison fails, and it fails hard
Freyja is a Van, and that means something. She belongs to a distinct group of gods, the Vanir, who fought a war with the Æsir and were incorporated by treaty and hostage exchange, arriving alongside her father Njörd and her brother Freyr. Whether that war records an actual historical religious conflict is an old and unresolved question, but the category is real and there is nothing corresponding to it in Greek religion. Aphrodite is not a member of an incorporated rival pantheon.
Grief. Freyja weeps tears of red gold for her absent husband Óðr, and travels among unknown peoples looking for him. Aphrodite grieves for Adonis, but that story arrives in Greek from the Near East and belongs to a lament tradition rather than to a marriage. The Norse goddess's defining private emotion is loss; the Greek one's is offence.
Fertility. Freyja's family portfolio is agricultural and prosperous — good seasons, peace, plenty — a Vanir specialism. Aphrodite has remarkably little to do with crops. Her Greek functions run to desire, seafaring, civic concord in some cities, and, in her celestial aspect, a philosophical idea of higher love that later writers made a great deal of.
Cult footprint. Aphrodite had major sanctuaries, festivals and a continuous documented worship across the Greek world for a thousand years. Freyja's evidence is largely literary, supplemented by place-names and by later Scandinavian folklore; there is far less to work with and any confident description of her rites is reconstruction.
The bigger problem: is Freyja even one goddess?
An old and still-live question is whether Freyja and Frigg were originally a single goddess who split, or two who partly converged. Both are associated with a husband who wanders, both are linked with a form of knowledge, and their names are not related though they are often confused. The evidence is genuinely inconclusive. Any comparison of "the Norse Aphrodite" that does not mention that the identity of its Norse term is disputed is overselling.
Why both were flattened
The reduction of these goddesses to a single attribute is a modern editorial habit with an identifiable mechanism. Nineteenth-century mythological handbooks organised material by function, one god per slot, which required deciding what each god was for. Aphrodite got love. Freyja got love, because the slot was labelled and she was the nearest fit. Everything that did not fit the label — armed cult images, half the battlefield dead, disreputable magic, a lost husband — became a curiosity rather than a defining feature.
The result is visible in modern reception. Freyja in contemporary fiction and in some modern religious practice is often reconstructed almost entirely as a goddess of love and beauty, and the battlefield claim is treated as a surprising extra rather than as one of the two things the earliest verse actually says about her.
Related arguments here
For the Norse afterlife arrangements this raises, see Valhalla and Elysium and those who come for you; for the goddess-lumping problem in its most extreme form, the great mothers. Individual entries: Aphrodite, Freyja, Inanna, Brísingamen, Venus.
Cats, foam, and a necklace with a hostile source
Did Freyja really have a chariot pulled by cats? It is in the prose account of Baldr's funeral, from the thirteenth-century Icelandic source, and appears nowhere earlier. The animals are described with a word for cats, and everything modern illustration adds — that they were lynxes, that they had names, that they were a gift — is later embroidery. Her boar, by contrast, is attested in verse.
Is Aphrodite's birth from sea foam the original story? There are two competing Greek accounts, and they were both current: one has her born from the severed genitals of Uranus falling into the sea, the other simply makes her a daughter of Zeus. The foam story includes a folk etymology of her name that linguists do not accept, which suggests the story was built to explain a name whose real origin was already lost.
Which Norse goddess is actually closest to Aphrodite? Arguably none, and the better cross-tradition match for Aphrodite is Inanna — the case for which is historical rather than structural, resting on transmission through Cyprus and the Levant. Comparisons that can point to a trade route are worth more than comparisons that can only point to a resemblance.
What is Brísingamen, and did Freyja really pay for it that way? It is her necklace or torc, mentioned in the eddic material and in the Old English Beowulf as a famous treasure. The story that she obtained it by sleeping with four dwarfs on consecutive nights comes from a late Icelandic manuscript, several centuries after conversion, in a text that is openly hostile to her — a piece of source-criticism usually omitted when the anecdote is repeated.