Wonder Woman is one of the most popular DC superheroes, and she holds the same position in the DCEU. With the release of her new solo film Wonder Woman 1984, one can expect that the Amazon princess will be busy. Not only will she face Cheetah but she'll also reunite with her lost love Steve Trevor who died during World War One.
However, if Wonder Woman wanted, she could easily find a new romantic partner. She has a rich history in the comics. Steve Trevor is her most famous love interest, but Diana has also had her fair share of other relationships - some of which could potentially make it into the DCEU as well.
Kaisa
It might be a surprise to those who only know of Diana's romance with Steve Trevor, but in some versions of the comics, Wonder Woman is more or less openly bisexual. The DCEU could introduce Kaisa or any other Amazon who had a crush on Diana. Kaisa doesn't want Diana to leave Themyscira and she says it would break her heart. It's a small moment but it still shows how dear Diana is to her fellow Amazons.
Keith Griggs
Another character who will be familiar only to comic-book readers is Keith Griggs. It's unlikely Keith will appear in the DCEU since Wonder Woman 1984 aims to bring Steve Trevor back. At best, Keith could hope for a brief cameo. The timing is right - Diana met Keith, who worked as an Air Force pilot, in the early 1980s. Their relationship was a bit problematic since Keith liked Diana more than Wonder Woman, but it was Diana who cut things off in the end, as she left Keith for Steve Trevor. With a bit of work, this relationship could fit in Wonder Woman's second solo movie.
Trevor Barnes
One of the things that are sympathetic about Diana is that she doesn't look down on non-powered people. She proved this once again when she dated Trevor Barnes who worked as a human rights advocate for the United Nations.
Barnes loved Wonder Woman but felt insecure because he was dating an actual demigoddess and a superhero on top of that. However, their relationship ended with Barnes's death, and since Diana had already seen one partner die in the DCEU, it's unlikely she would go through this again, at least not anytime soon.
Aquaman
And now it's time to focus on characters who are already in the DCEU alongside Diana. Aquaman and Diana were a thing in the alternate timeline in the comics called Flashpoint. In the DCEU, Arthur is dating the princess Mera. However, he did confess his respect for Wonder Woman's fighting skills and his admiration for her beauty in Justice League. And Diana seemed flattered and amused by his interest, not insulted, so these two could potentially work under the right circumstances.
Batman
From the moment Diana appeared in Batman v Superman, the chemistry between her and Bruce Wayne was obvious... even before he knew who she really was. These two later became friends in Justice League and spent quite a lot of time together. It looks like Ben Affleck is done with playing Batman, but if he wasn't, he and Wonder Woman could become an item. They certainly flirted with this notion often enough in the comics. Batman kissed Wonder Woman in the comics. She expressed her interest in him in an animated TV show but Batman shot her down at first because he was emotionally constipated.
Superman
They rarely ever interact in the DCEU, but in the comics, Superman and Wonder Woman were a couple for quite some time. It was a controversial move for many fans since Superman and Lois Lane are such an iconic couple, but Wonder Woman and Superman dating also makes sense.
They're in many ways similar, both have godlike powers, are inherently good and their primary desire is to help people. They even got married and had children in some alternate realities. It's unlikely the DCEU will hint at this couple but it wouldn't be as far-fetched as some might think. Plus, Gal Gadot and Henry Cavill are also close in age, Gadot is 35 and Cavill is 37, so at least age-wise, the relationship could work.
Harley Quinn
Finally, one of the more bold plots the DCEU could offer would be if it paired Wonder Woman with Harley Quinn - perhaps on a shared mission that would force them to cooperate? Harley Quinn is even more openly bisexual in the comics than Wonder Woman is since she dated Poison Ivy. This relationship also got a mention in Birds of Prey (2020) where Harley briefly mentions that Ivy dumped her.
But what does it have to do with Wonder Woman? Harley is her big fan in the comics, and when she learned that Wonder Woman's enemies were after her, Harley made it her mission to help, went into Wonder Woman's apartment, and it got even more complicated from here. Seeing the two women interact in the DCEU would be hilarious, but once again, it's unlikely to happen anytime soon, if at all.