In alphabetical order (with issue and date of first appearance).
Separated in chronological clusters, by major periods in the publication history of the Wonder Woman comic book.
Characters who appeared before the continuity-altering series Crisis on Infinite Earths.
Queen Desira - Venusian queen.
Lila Brown - Steve Trevor's secretary, who instantly disliked Diana Prince, she was killed by Doctor Psycho.
Eve Brown - Lila Brown's sister.
Holiday Girls - Etta Candy's Beeta Lambda sorority sisters at Holiday College.
Oscar Sweetgulper - Etta Candy's spindly, nerdy boyfriend, from Starvard College.
Dean Sourpuss - the grim, heavy-handed dean of Holiday College.
Professor Zool - brilliant, though absentminded, eminent scientist at Holiday College.
Hard Candy - Etta Candy's father, who owns a ranch.
Sugar Candy - Etta Candy's mother.
Mint Candy - Etta Candy's brother.
Draska Nishki - Government spy and blackmailer.
Bird-Boy - (real name: Wingo - AKA Birdman) A suitor of Wonder Girl, and a member of a race of bird people.
Mer-Boy - (real name: Ronno; alias: Manno) An Atlantean suitor of Wonder Girl.
Mr. Genie - (real name: Genro) Wonder Tot's magical friend, from the 5th Dimension of Zrfff, the home dimension of Mister Mxyzptlk.
Cathy Perkins - teen runaway who worked in Diana Prince's boutique
Drusilla - An Amazon who helped Diana save Themyscira from an attack invasion by Ares
I Ching - blind Chinese mystic who became Diana Prince's mentor
Jonny Double - down-on-his luck private investigator
Tim Trench - shady private detective
Tony Petrucci - neighborhood supporter
UN/New York
Justice League of America - Group of super-heroes formed to face new threats against mankind with Wonder Woman as a founding member
The Kravitzes - Abner and his mother owned the apartment building Diana and Steve Trevor lived in
Morgan Tracy - head of the UN Crisis Bureau, later revealed to be the Prime Planner of the Cartel, which was hired by Kobra to kill Wonder Woman
Tod - neighbor in Diana's apartment building
Nubia - Wonder Woman's sister stolen by Mars as an infant
NASA/Houston
Mike Bailey - fellow astronaut trainee who dated Diana and was secretly Ten of the Royal Flush Gang
Stacy Macklin - fellow astronaut trainee, who later became Lady Lunar
Conrad Starfield
General Novak
Washington, DC
Atalanta - leader of a lost tribe of Amazons who live in the Amazon River jungle
Glitch - alien "gremlin" only Steve and some children could see
Keith Griggs - hotshot Air Force major who joined the Special Assignments Bureau and was romantically interested in Diana Prince
Lauren Haley - beautiful and highly competent Air Force lieutenant hired by Special Assignments
Howard Huckaby - hopelessly clumsy, wonky aide to Sen. Covington, and Etta's boyfriend
Lisa Abernathy - daughter of Sen. Abernathy, and network news reporter covering Washington while conducting secret affair with frequent source, Sen. Covington
Mother Juju - old mystic
Sen. Russell Abernathy - disgraced former senator who was landlord for Diana and Etta
Sen. Brad Covington - powerful, media-savvy senator, chair of subcommittee on Central American affairs, with an agenda to aggressively investigate Special Assignments at the urging of a mysterious campaign donor with a grudge against Gen. Darnell; secretly, lover of TV news reporter Lisa Abernathy, unknown to his wife, Mona
Sofia Constantinas - former terrorist who was invited to live among the Amazons
Brian Elliott - Computer genius who attempted to become a supervillain but was slowly persuaded to become a friend and ally
Camille Sly - long-lived but still spry former actress who was known in her day as the "Female Fairbanks" for her roles in swashbuckling movies, who rented rooms in her boarding-house to both Diana and Donna Milton
Donna Milton - believed herself to be a devious lawyer, always looking out for her own selfish interests and greed, who was the lover of Ares Buchanan and a spy in Wonder Woman's life but gradually became Diana's friend, until Diana deduced that she was Circe, so submerged into the Donna Milton persona that she had forgotten her real identity
Ed Indelicato - inspector on the Boston police force
Isabelle Modini - Boston police officer who initially held a grudge against Diana for leaving her hanging above a street while Diana attempted to talk down a heavily armed villain, but who became Diana's friend after that villain later gave up his own life to save hers.
Julia Kapatelis - professor and archaeologist who became Diana's mentor in Man's World
Micah Rains - slacker detective whose "office" was merely a barstool until Diana became his partner
Myndi Mayer - public relations executive who was Diana's representative
Vanessa Kapatelis - daughter of Julia Kapatelis
Helena Sandsmark - Gateway City museum chief and mother of Cassie Sandsmark, the new Wonder Girl.
Jason Blood - mortal host of The Demon and paramour of Helena Sandsmark.
Mike Schorr - police officer and one time love interest.
Wonder Dome - semi-sentient polymorphic entity.
Harold Champion - Heracles, in a new identity, seeking redemption.
Justice Society of America - Hippolyta, displaced in time, would join the JSA and carry on a relationship with Ted Grant.
Sphinx - A mythical creature living on Paradise Island that offered counsel to Wonder Woman.
Chiron - Legendary Centaur living on Paradise Island that was a trainer of heroes in ancient times.
Pegasus - Legendary winged horse that makes his home on Paradise Island and progenitor of the Amazons' winged steeds.
Nu'Bia - First champion of the Amazons and guardian of Doom's Doorway.
Alana Dominguez - secretary for Themysciran embassy staff
Ferdinand the Minotaur - head chef of Themysciran embassy
Io - Amazons chief weapons-mistress
Jonah McCarthy - young attorney hired to join staff of Themysciran embassy, but secretly spying for the shadowy Checkmate organization
Leslie Anderson - co-founder of Cale-Anderson Pharmaceuticals, and doctor who healed Vanessa Kapitelis of the cybernetic implants that had transformed her into the Silver Swan
Peter Garibaldi - press secretary for Themysciran embassy and father of Martin and Bobby Garibaldi
Rachel Keast - legal staff of Themiscyran embassy
Trevor Barnes - Diana's boyfriend, and UN staffer
Harbinger - Formerly an agent of the Monitor and member of the New Guardians, Harbinger would join the Amazons at some point and befriend Supergirl
Agents of the D.M.A.
Gorilla Warriors - albino gorillas from Gorilla City with superpowers
Nemesis - agent with talent for impersonation
Sarge Steel - head of DMA
Kāne Milohai - The deity Wonder Woman took as her patron saint to infiltrate Paradise Island, her presence banned by divinity. Zeus would slay him and use his heart to give form to Achilles
Warkiller - Achilles, resurrected with the heart of a slain god, tasked by Zeus to lead the Thalarions
Pele - Milohai's daughter that became Wonder Woman's patron after the demise of her father at Zeus' hands
Post-Flashpoint and New 52
Characters who appeared after the continuity-altering series Flashpoint and the continuity-reboot, the New 52.
Lennox - a British super-soldier, who was Wonder Woman's older half-brother. Lennox, who can transform himself into living, marble-like stone, is the father of Cassandra Sandsmark (Wonder Girl). The first of the half-mortal siblings to reveal himself to Wonder Woman, Lennox was Diana's most trusted ally, before his apparent death at the hands of another half-brother, the evil First Born.
Zola - young woman from Virginia told by Hermes she is carrying Zeus' child.
Manny, David, and Chris - members of Steve Trevor's Echo-Alpha team.
Leah - Etta's personal aide at The Picket.
Characters related to Wonder Woman but were not supporting characters in the Wonder Woman comic book.
Fury (Helena Kosmatos) - Member of the Young All-Stars during WWII, Fury would join the Amazons after meeting a time-displaced Hippolyta.
Fury (Lyta Trevor Hall) - Pre-Crisis: the daughter of Earth-Two's Wonder Woman and Steve Trevor. Post-Crisis: daughter of Fury and goddaughter of Hippolyta visited annually via time travel by her godmother.
Justice Society of America - Group of masked heroes Wonder Woman joined as their secretary.
Marvin White - The son of Diana Prince, a nurse who lent her identity to Wonder Woman. Marvin would later join the Junior JLA.
Supergirl - Pre-Crisis, Supergirl was embraced as an honorary Amazon. Post-Crisis: Inexperienced at wielding her awesome powers, Supergirl underwent training on Themiscyra to develop her abilities and learn about combat by the Amazons (adopted as their sister).
Wonder Woman supporting characters created in other media, with no appearances in previous comics.
Some supporting characters from the comic books have made an appearance, or appearances, in other media featuring Wonder Woman.