Can Wonder Woman Lift Thor's Hammer?
Diana of Themyscira: warrior, princess, demigod, heroine. Much of her illustrious legacy in comics has had her act not just as savior to the little man, but also as arbiter and conscience for her fellow heroes when they fall short or are feeling unfit for the task at hand. It's no overstatement to describe Wonder Woman as an ultimate avatar of justice and peace, motivated by a pure desire to right wrongs and help literally anyone in need. All of the above serves as an excellent resume for worthiness as Thor's hammer Mjolnir unspecifically requires.
A surface-level comparison between Thor and Wonder Woman suggests that the Amazonian may actually be more worthy than the God of Thunder to wield Mjolnir — Thor's trigger finger is itchier than Diana's, and Asgardians in general are certainly more morally gray than the Amazons of Themyscira, too. Setting aside the obvious barrier of separately published universes between them (Wonder Woman's with DC and Thor's with Marvel), just how well could Diana measure up to the standards of Mjolnir and potentially harness its power? Can Wonder Woman lift Thor's hammer?
What does worthiness actually mean?
The exact words on Mjolnir read, "Whosoever holds this hammer, if he be worthy, shall possess the power of Thor." No greater context is really available besides the content of comics canon, which is slippery on its best day. Objectively bad people have used Mjonlir — like Loki, for example, though he cheated and used a spell from Scarlet Witch and Doctor Doom to circumvent The Rules. This both suggests the mystical hammer is flexible to choices (and sneakiness around technicalities) within individual circumstances and that its definition of "worthiness" isn't strictly limited to whether or not any one character can conceivably fit within the reductive box of lawful-goodness.
Superman himself was only permitted to heft the hammer for exactly one fight and was unable to pick it up again once hostilities ceased. That's a wise assessment — while there are times, perhaps, Superman needs a circumstantial boost for the cause of good, he probably shouldn't be able to just casually haul such a weapon around. He tends to get it in his head that he's the only arbiter of truth, justice, and the American way.
Another great example is the time the Awesome Android was permitted to wield Mjolnir. While inherently unqualified to use the hammer on fair and square terms, the Awesome Android utilized his ability to copy others' qualities and made himself worthy. He didn't copy Thor's powers but rather Thor's innate character, though he could only do this for an hour at a time. It's a mystery how exactly one enumerates how to copy such a philosophical concept, but this is comics, so don't think about it too hard or look too deeply for rationality.
Looking at the Marvel Cinematic Universe canon, the argument can even be made that Thor's father Odin, as the man who made Mjolnir in that continuity, redefined what worthiness is to the hammer based both on Thor's actions in his first movie and on the historical colonial attitude Odin once adopted until Hela was removed. Thor had to prove his worthiness over again to a new set of standards. Like a lot of tropes surrounding the usage of magic across all media, the rules around Mjolnir are just vague and loop-holey enough to permit a whole bunch of circumstances.
What does that mean specifically for Diana and her potential ability to lift Thor's hammer? It's a solid "maybe" for any day ending in Y. It's even probable, because no matter what, Wonder Woman is an objectively good person devoted to justice, which is probably a better standard to measure in the case of Mjolnir than peace. It's a hammer — that's a weapon, no matter how you slice it.
The time Wonder Woman lifted Mjolnir
The simplest fact of the matter is that there is indeed one discrete example of Wonder Woman wielding Mjolnir to which we can point – though it obviously has to carry the caveat of being a special case and therefore extra-canonical (if you happen to care about that kind of thing).
In 1996, DC and Marvel ran a short crossover series entitled DC versus Marvel Comics and in it, Diana picks up Mjolnir after it appears (without Thor) through a wormhole between their worlds. But after hoisting the hammer and appreciating the power it imbued upon her, Wonder Woman decides it actually isn't fair to use the hammer during the fight she's in with Storm from the X-Men. Thus, she relinquishes Mjolnir and loses the battle as a result.
Ostensibly, the complete truth here is that Wonder Woman can lift Mjolnir but she's too good for it, and will voluntarily discard it because the abilities it gives her are impermissibly powerful. If we were living as a semi-sentient mythical hammer capable of choosing wielders by a moral standard, we'd be a little miffed, honestly. Well fine, Diana, if you wanna be self-righteous about it, go ahead. Jeez.