Although acknowledged as bisexual by several of her most prominent writers in the modern era of comics, including Greg Rucka and Gail Simone, there has been much discussion revolving around Wonder Woman and whether we'll ever see her in an explicitly same-sex relationship. While her origins date back to the '40s and are quite literally based around her being born and raised on an island where only women are allowed, we've gone more than 70 years never seeing much in the way of on-page confirmation of her status as an LGBTQIA icon. Subtext so strong that it tends to jump off the page at you: yes. An openly romantic relationship with a woman: no.
The reasons for this are myriad, and certainly should be subject to valid criticism from any LGBTQIA person who feels slighted. On the other hand, it's worth mentioning that even though Diana might never have the amazing on-page or onscreen LGBTQIA love story we want her to have, there are many other queer Amazons in Wonder Woman's mythology that don't receive much attention.
In Greek mythology, the Amazons were known as the followers of Ares and Harmonia. While most people recognize Ares as being synonymous with war, Harmonia was the god representing peace. As with some gods, she had an equal but opposite half in Discordia, a god representing strife and discord. The juxtaposition of being ruled by both war and harmony is a central theme for most stories about the Amazons. Most mythology around Amazons was written by men hundreds or thousands of years ago. There are constant references to Amazons being physically similar to men, not to mention the ridiculous proposal that they actually were men (because women would never be capable of fighting in a war), in-depth explanations of how they continued to have children, and, of course, the prevalent and completely nonsensical myth that each Amazon had one of her breasts seared as a child in order to be able to shoot a bow. Obviously, a basic understanding of anatomy disqualifies this as being a necessity, but it indicates the general sense of exaggeration around the Amazonian myth.
This legend was reworked by William Moulton Marston when he was inspired by the suffragette movement to team with his wife Elizabeth and create a female superhero, one who would eventually be known as Wonder Woman. The undercurrent of sapphic longing and bondage that runs through early Wonder Woman stories has been written about at length, but essentially Marston's personal belief system revolved around the concept that men should resign from their position of authority and allow themselves to be gently dominated by women, and the comic certainly reflected that notion during the years it was under his creative control.
As is typical with adaptations, the many creators (Marston included) of the Amazons of DC Comics have changed the story significantly from the early legends of Greek mythology. In comics, Hippolyta is the leader of the Amazons and the mother of Wonder Woman. Intended as a lesson for mankind, the Amazons were introduced by the gods as a bridge of understanding. However, Hercules was hurt by taunts that he could not tame the Amazons and challenged Hippolyta to a fight, which she won. Regardless, he and his followers rapidly enslaved the Amazons, causing them to rebel and create their own secret world on Paradise Island. It's hard to say where we're at as of today with this mythos, given that Wonder Woman and most of her DC chronology have been rebooted many, many times, but, essentially, Hippolyta formed Diana out of clay because she wanted a daughter so badly.
In mythology both modern and ancient, there is a consistent emphasis on the Amazons and their dealings with men, despite those dealings being the very least interesting thing about them. Baffled by a society of women, male writers have leaned on a multitude of story devices to separate Diana from her Amazonian heritage. In response, some writers, such as George Perez and Phil Jimenez, have gone to some lengths to show what life on Paradise Island would be like in hopes of getting Diana back to her roots, but there has been shockingly little focus on just how queer this all-woman island would be, separate from the rest of mankind for thousands of years.
If Diana ever had a girlfriend, the strongest case would be for Mala. In the early days of Wonder Woman comics, Mala was referred to as Diana's best friend, and they seemed to be together all of the time. Even after Diana went to the world of men, Mala constantly tried to join her, only to be refused either by Hippolyta or Diana herself. Mala was perhaps even more naive than Diana, claiming not to understand women or men outside of Paradise Island very well. Although it changes per incarnation of the story, Mala was either Wonder Woman before Diana or challenged Diana for the role of Wonder Woman, which Diana eventually won. For a time, she even had her own invisible jet, similar to the one Wonder Woman flew for several decades. Regardless of the specifics, she and Diana have always been close. When they appear together on-panel, they tend to be touching each other, looking into each other's eyes, and generally attempting to comfort one another. In the original stories, when Diana finds Steve Trevor, it is Mala who is with her, and Mala who wants to accompany her when Diana leaves Paradise Island.
In Grant Morrison's Wonder Woman: Earth One, we are introduced to a jealous take on Mala, who is confirmed to have been Diana's lover but despises Steve Trevor for taking Diana away from her. The trope of the bitterly jealous lesbian is pretty tired, but, in all fairness, Diana did pretty much steal her title and her plane before ditching her for Steve Trevor, so Mala had pretty valid reasons to be upset with her. At any rate, Mala of Earth One is a far cry from the tender, well-meaning friend we know from the original stories. Although she's been shunted to Limbo many times over, I have incredibly fond memories of the early versions of Mala and am always interested in her returning to comics as the tough queer femme she's implied to be.
The next example of an out queer character is Nubia, who was later renamed Nu'Bia and who may or may not exist in current DC continuity. Nubia is a hugely important character, despite seldom getting her due, because she's one of the first black female superheroes. Nubia's first appearance was in 1973, in a story where she appeared dressed head-to-toe, bested Wonder Woman in battle, announced herself as the true Wonder Woman, then took off her helmet to reveal that she was a black woman. Coincidentally, Nubia ruled an island of all men and bore the same origin story as Diana, being made from clay by Hippolyta. She was later reimagined as Nu'Bia, but possessed most of the same characteristics.
Nubia has appeared mostly in the context of being Wonder Woman's equal, and she often has a female lover. In Earth One, she appears to be Hippolyta's lover, which is weird if you read her Golden Age appearances in which she is Hippolyta's daughter. Equally strange, in the comic Wonder Woman '77 Meets the Bionic Woman Nubia marries Fausta Grables, an ex-Nazi who was prominently featured in an episode of the TV series before denouncing Nazism and joining the Amazons. Nubia's relationship choices might not be the greatest, but she is a character long overdue for a more prominent role in DC.
Although she didn't make her first appearance until the '80s, Philippus has since become a vital character. At Hippolyta's side from the early days even before Paradise Island, this is a woman whose loyalty knows no bounds. She became the general of Hippolyta's Amazonian army and accompanied Hippolyta as her protector for centuries. In most versions of Wonder Woman since her debut, Philippus has served as a second mother to Diana.
Again, although it is seldom confirmed, it is generally accepted as canon that Hippolyta and Philippus were romantically involved with one another at some point throughout the years. Philippus is one of the very few Amazons who has the courage to call out some of Hippolyta's worst decisions, and she's also the only one Hippolyta ever seems to truly listen to. In fact, it is partially her disregard for Philippus' counsel that marks her as an imposter in the story Amazons Attack! Despite being addressed only briefly, in Rebirth Hippolyta and Philippus are confirmed to be lovers.
Etta Candy is another character who's been around since the Golden Age but was recently revamped in Rebirth. Originally appearing as a white blonde woman, Rebirth's Etta is black, and while her bisexuality was addressed only in alternate reality takes, she was confirmed to be part of the LGBTQIA fam. It might have taken decades for writers to work it out, but the world deserves a queer Etta Candy.
The character of the Cheetah existed nearly as long as Wonder Woman herself, making her first appearance as a wealthy, jealous socialite early on in the series. Years later, she was replaced with Barbara Minerva, an archaeologist who went seeking a god and was granted powers at a terrible cost. In Greg Rucka's most recent run on Wonder Woman, Minerva was driven to devour men after being cursed by the god. When cured, she tries desperately to redeem herself, falling tragically short due to outside forces. In Rucka's Wonder Woman, Etta Candy and Barbara Minerva don't exactly get a fully fleshed-out relationship, but they do flirt with each other quite a bit, and it's extremely cute. Here's hoping we'll see a thorough exploration of that dynamic going forward.
There will probably always be more observations about queerness in Amazon and Wonder Woman mythos than there will be actual LGBTQIA representation, but it can't be said that it doesn't exist.