LGBT characters

A number of people have been identified as (or implied to be) lesbian, gay, bisexual or transgender (commonly abbreviated LGBT).

Lesbians

 * Patty Bouvier - Almost married Veronica.
 * Verity Heathbar - Leaves her husband Charles for Patty, who says that they were brought together by their hatred of Homer.

Hinted to be Lesbian

 * Martha - hinted as being attracted to the assistant librarian.
 * Librarian - hinted as being attracted to Martha.

Openly gay characters

 * Comic Book Gay - Comic Book Guy's gay cousin. He likes "a certain kind" of comic books.
 * John - A nostalgia store owner who befriends the Simpson family.
 * Roscoe - Manager of the Ajax Steel Mill. He and his workers are all gay, and at breaks, they turn the mill into a gay nightclub.
 * J&J Construction Contractor - A builder who was employed to remodel the Simpsons' kitchen after Homer's failed attempts.
 * Grady and Julio - Were a couple when Homer roomed with them; they later broke up.
 * Thad - Marries Julio (with Homer as the officiant) subsequent to Julio's and Grady's breakup.
 * Grizzly Shaun - Becomes interested with Moe.
 * Dewey Largo, in season 22, episode eleven - Flaming Moe, he announces to his music class that he is running away with the love of his life, who is a man.
 * Waylon Smithers- There are numerous references to Smithers' orientation (or at least his fixation on Mr. Burns) and his efforts to keep it a secret. However, a blatant example occurs when Smithers boots up his home computer and an animation of Mr. Burns appears, saying (in obviously cobbled-together sound clips), "Hello, Smithers. You're quite good at turning me on." Smithers then says to Lisa (who was standing behind him), "Um, you should probably just ignore that." Smithers was first openly gay in Flaming Moe, when he helps reopen Moe's tavern as a gay bar.
 * Dewey- A boyfriend of Dewey Largo.

In the closet

 * Unnamed Latino Man - When he saw Homer's graffiti tag of "El Homo", he said, "If only I had your courage, Señor."
 * Unnamed smoking man - Moe tried to steal his watches, but when the man noticed him, Moe said that he had been just coming on to him. The man took Moe's hand and said that they could go back to his place.
 * Raoul - Women disgust him and becomes interested with Abraham Simpson.
 * Stuart - A close friend to Waylon Smithers.
 * Gay Colonel - Colonel who dates with Hans Moleman.

Hinted to be Homosexual

 * Lenny Leonard - Sometimes hinted as being attracted to Carl.
 * Carl Carlson - Sometimes hinted as being attracted to Lenny.
 * Rod and Todd - Ned Flanders gave Bart Simpson money for not outing them in (Bart to the Future),  they had moustaches and were seen refurbishing furniture in denim shorts and white sleeveless shirts.
 * KarlKissesHomer.JPG[[Karl]] - Kissed Homer on the lips after stating that his mom taught him to never kiss a fool. However, it should be noted that Karl is implied to be of German origin, and men kissing men doesn't necessarily equate to homosexuality as much as just respect in some European countries. Karl also patted Homer on the behind after giving him a pep talk, but in the context of the situation, it could easily be considered a comradely gesture rather than an affectionate one. Further clouding the issue is that Karl was friends with the women in the power plant's typing pool, and, after being fired, made a point of returning to say goodbye to them. However, it isn't known whether he was romantically involved with any of them. There is a lot of ambiguity surrounding the issue of Karl's sexual orientation, and not enough information to definitively settle the question.Though it will always be a question
 * Llewellyn Sinclair - Is seen in the crowd of gays.

Transsexual

 * Judge Constance Harm - Indicates that she was born male.
 * Brunella Pommelhorst - Takes a leave of absence from teaching gym at Springfield Elementary School; says she will return next semester as Mr. Pommelhorst, the new shop teacher after a sex change to a man.

Hinted to be Transsexual

 * Helen Lovejoy - The Parson tells Reverend Timothy Lovejoy that he "remember[s] when [Helen Lovejoy] was Helen Schwartzbaum. In fact, I remember when she was Harold Schwartzbaum." This is very unlikely, due to her and Tim having a daughter together, as well as a flashback clearly depicting her as a little girl.
 * Waylon Smithers - Smithers hinted at possibly being transgender when Marge was selling prescription medication at a garage sale and he bought bottles of estrogen for "a friend...who's trapped in the body of another friend." He also hints at transvestite tendencies in "When You Dish Upon a Star" when he asks Kim Basinger where to get red pumps similar to those her character wears in LA Confidential.
 * Dewey Largo - Sought gender reassignment surgery from Dr. Nick, but because Nick had the surgery files mixed up, Largo ended up getting an operation intended for Moe, which made him shorter.
 * Frank Simpson - Homer Simpson's history about Frank Simpson implied that Frank changed his gender in 1976.
 * Martin Prince - In Holidays of Future Passed, Adult Lisa gets a Facebook-like friend request from Adult Martin Prince, now known as Marcia Princess. [This could be canon or non.]

Bisexual

 * Lady Gaga - She's openly bisexual in real life (which is hinted in the hit single "Poker Face") and even kisses Marge Simpson in Lisa Goes Gaga, much to Marge's surprise.
 * Rainier Wolfcastle - openly bisexual since he has his early gay porn films located within his bedroom.

Hinted to be Bisexual

 * Duffman - Slept with Titania, who was competing in a bartending contest that he was judging. However, Bart mentions that Duffman is supposedly in a long-term gay relationship after seeing him dining with Booberella. He is later in a relationship with Julio. It should be noted, however, that there are several different actors portraying Duffman, and not all of them necessarily have the same sexual orientation. [It has also been noted that Duffman has clones]
 * The Sea Captain - Apu delivers pornographic magazines to keep the Sea Captain's crew from resorting to situational homosexuality for about ten minutes, at least. However, the Captain is also seen taking pictures of Selma and Patty in the nude to cope with being out at sea.
 * Santa's Little Helper - Intrigued by male dogs at the Springfield Gay Pride Parade. However, he mated with both She's the Fastest and Rosa Barks, both of whom were definitely female as both union produced puppies.
 * Ralph Wiggum - In The Simpsons Movie, he declares "I like men now!" after seeing Bart naked on a skateboard. However, Lisa Simpson was his first crush. It should be noted, though, that nothing Ralph says about himself is reliable, since his understanding of everything is questionable.
 * Milhouse Van Houten - Noted as having "flamboyantly homosexual tendencies" by Dr. J. Loren Pyror, but has a long-standing crush on Lisa Simpson and has dated other girls.
 * Martin Prince - Generally effeminate and was shown to have a crush on Ralph Wiggum at one point [citation needed]. Accused of being gay by Nelson and protests, "I'm not anything yet!"; has a male robot boyfriend in the future. On the other hand, he did have an attraction to Princess Kashmir on seeing Bart's photo of her dancing with Homer, even referring to it as being "quite exciting" and calling her a "sexy lady" when he asked Bart who she was. When he imagines himself as a basketball player in Replaceable You he is holding hands with both a male and female cheerleader.
 * Lisa Simpson - In the episode "Holidays of Future Passed", a montage of photos were featured to show a glimpse of whats to come for the Simpsons family. Lisa Is shown intimately holding hands with two women in one photo, then with a different woman in another photo. She is later shown married to Millhouse Van Houten and having a child with him. She also was suggested to explore at a college of the 7 sisters. Also in the episode Gorgeous Grandpa, Homer was flipping through the reality shows to Lisa's disgust. However, when Homer and Lisa keep flipping through channels and sees a reality show on gay marriage she says 'Well' and thinks about it.
 * The first, the second and the third of The Cool Moms - They all are married and have sons, but when Marge abandon the club, they start kissing and hugging each other.
 * Shauna - She is implied to be bisexual as Dolph said that she invited 200 guys and 7 girls to make out with her via a SpringFace message.