King of the Hill is an American animated sitcom created by Mike Judge and Greg Daniels. The main characters are Hank Hill, Peggy Hill, Bobby Hill, Dale Gribble, Bill Dauterive, Jeff Boomhauer, Luanne Platter, Nancy Gribble, Joseph Gribble, Kahn Souphanousinphone, Minh Souphanousinphone, Connie Souphanousinphone, John Redcorn, Cotton Hill, Didi Hill, Buck Strickland, Lucky Kleinschmidt, and Brian Robertson are all listed first followed by recurring and guest characters.

Hank Rutherford Hill (voiced by Mike Judge) is the main protagonist who proudly sells "propane and propane accessories" as the assistant manager at Strickland Propane. Hank's enthusiasm for his career is not usually shared by other characters in the series. The episodes "Movin' On Up" and "Chasing Bobby" show Hank escaping from his troubled home life by working on his lawn and truck when times are tough. Hank resembles—in both voice and appearance—the Tom Anderson character from Beavis and Butt-Head, who is also voiced by Judge. Hank is usually a well-meaning father, but is often confused and anxious towards modern trends and the antics of his friends and family members. He suffers from a narrow urethra, which made Bobby's conception difficult. Hank is uncomfortable with public displays of intimacy with his wife and son. He has a very difficult time saying "I love you" to any member of his family, as he thinks it is unmanly. Hank's trademark exclamation when surprised, angered or discomforted (sounding like "Bwaaa!") and his phrase "I tell you what" ("what" in his dialect being pronounced "hwaht") are running gags on the series. Hank is always faithful, friendly, firm, reasonable, well-read, and hard-working. Much of the series revolves around Hank's desire to do the right thing compared to much of the rest of the people around him who would rather cheat, lie or exploit; however, the people who try to take advantage of Hank tend to regret it because Hank is tougher and a lot shrewder than they thought. His favorite sports team is the Dallas Cowboys (he never expressed much interest in the NBA and Major League Baseball teams in the Dallas-Fort Worth area) though he has indicated that being a Houston Texans fan isn't out of the question because they aren't in the same NFL conference as Dallas and would only require any rooting interest decisions if the Cowboys and Texans somehow faced each other in a Super Bowl (a scenario that Hank looks forward to with hope akin to religious reverence). Hank is a proud Texan, having grown up there. He was, however, born in a ladies room at Yankee Stadium, and spent the first three days of his life in New York City.

Margaret J. "Peggy" Platter Hill (née Platter) (voiced by Kathy Najimy) is Hank's wife. Peggy was born in Montana and raised on her family's cattle ranch, her strained relationship with her mother being a source of drama for her. Peggy is a substitute teacher in Arlen, Texas, specializing in teaching Spanish despite having a terrible grasp of the language. Peggy resembles in appearance the Marcie Anderson character from Beavis and Butt-Head. Peggy is also a mediocre freelance newspaper columnist, notary public, an exemplary softball pitcher, a Boggle champion, and has started a career in real estate. She has a habit of adding or changing ingredients to ordinary dishes and then naming them after herself. "Spa-Peggy & Meatballs" and "Apple Brown Peggy" are examples. Peggy is very self-conscious about her larger-than-normal feet (size 16 ½ on the left, 16 on the right). Despite boasting of her intelligence, she has been the victim of manipulation, such as being conned out of $2,500 for a phony degree, indoctrinated into a homogeneous cult, and tricked into a pyramid scheme selling Herbalife inspired products. She has brown hair and typically wears glasses, an aquamarine sleeveless shirt, and denim culottes, but often wears different outfits.

Robert Jeffrey "Bobby" Hill (voiced by Pamela Adlon) is Hank and Peggy's husky son who starts out the series at 11 years old, and later turns 13 years old. He is best friends to Joseph and Connie. Although friendly, gentle, lovable, and generally well-liked, he is often prone to making bad decisions. He wants to seek fame as a prop comic and move to New York when he is older. Bobby displays little interest in gender roles and, although superb at golf and target shooting, dislikes team sports, often taking such classes as Home Economics and Peer Counseling instead of more traditionally "masculine classes", much to Hank's chagrin. Although many (including Hank) tend to typify him as "not right", he is romantically successful, dating Connie and other girls throughout the series.

Dale Alvin Gribble (voiced by Johnny Hardwick from 1997 to 2025, Toby Huss from 2025–present) is the Hills' chain-smoking neighbor who is also an insect exterminator among various self-appointed occupations. His physical appearance was modeled after Hunter S. Thompson. Hank considers Dale a close friend, but he often gets annoyed with his schemes and conspiracy theories. Dale is paranoid about any government activity and frequently uses the alias of "Rusty Shackleford" to operate without revealing his true identity, including receiving unemployment compensation payments as Rusty. Dale is the president of the Arlen gun club and is a licensed bounty hunter. He possesses a vast collection of guns from pistols to automatic weapons and is an ardent defender of Second Amendment rights. Despite being a firearms aficionado, his aim is relatively poor and despite being knowledgeable in military matters, he is the weakest, physically, of the main cast and is an abject physical coward. He is an avid UFOlogist. It is heavily implied that his wife, Nancy, has cheated on him with John Redcorn for 14 years, and his son Joseph, who strongly resembles John Redcorn, is not his biological son; despite Dale's conspiratorial tendencies, he never suspects his wife of infidelity although he did suspect an alien to be his biological father. Everyone else knows of Joseph's paternity but chooses not to tell Dale because of his total obliviousness, the loving, trusting relationship he has with Joseph and Nancy, and the fact that Dale is more of a father to Joseph than John Redcorn. In season 14, Dale was previously elected the Mayor of Arlen but won with only 9% of the vote after running against a wide pool of candidates; as an "election denier denier", Dale stood down 36 hours after his election, saying that he had no faith in a system that would allow him to get elected.

Sgt. William "Bill" Fontaine de La Tour Dauterive (voiced by Stephen Root) is the Hills' overweight, divorced, clinically depressed neighbor. He grew up in Louisiana with his cousin Gilbert and speaks Creole and English. He was formerly a rugged star fullback on Arlen High's football team where he set the school record for touchdowns and was nicknamed the "Billdozer", and is now a sergeant barber in the United States Army. While his job mostly consists of shaving recruits, he is in fact an extremely talented barber who is able to replicate Hank's signature flattop when Hank's longtime barber became senile. Bill once had a bright future in the Army wanting to be a tanker, but ended up ruining his life after marrying the promiscuous Lenore. Bill is something of a masochist and is often attracted to people who abuse him; after suffering under his father and Lenore, Bill has an almost complete lack of self-worth. He obsesses about his ex-wife, and his loneliness is a running gag on the series. He frequently tries to flirt with and win over Peggy, who alternates between being disgusted and dismissive at his presence or recognizing his essential kindness and harmlessness and being nice to him. Despite coming across as a loser, however, Bill has enjoyed several romantic successes (or near-successes), including romances with Kahn and Luanne's mothers, former Texas governor Ann Richards, and the young widows of two of his dead cousins. He is named after executive producer and writer Jim Dauterive. Between seasons 13 and 14 but before the COVID-19 pandemic, the Army had forced Bill to take an early retirement, leading to Bill to befriend Brian's friends at an all-black barber shop so he could continue cutting hair. However, once COVID hit (as well as the ensuing lockdowns), Bill became an unkempt recluse, gaining significant amounts of weight and never shaving or cutting his own hair, completely relying on delivery services such as Amazon, DoorDash, Uber Eats & Instacart, and never leaving his house—to the point where Netflix issued a wellness check once he ran out of programs to watch on Netflix—even after the pandemic ended until Hank and Peggy return home.

Jeffrey Dexter "Jeff" Boomhauer III, referred to as simply Boomhauer, (voiced by Mike Judge) is a slim blonde ladies' man and neighbor of the Hills, whose mutterings are hard to understand to the audience but easily understood by his friends. A running joke is when his friends fail to understand him for some reason other than his incoherence, such as reading out loud the legalese in a contract. His speech is usually heavily littered with the phrases "dang" and "dang ol'". Boomhauer can mumble his words, but he sings clearly and speaks other languages clearly (mainly French and Spanish). Boomhauer is a classic-car aficionado and owns a 1969 Dodge Coronet Super Bee (in high school, he owned a late 1960s Ford Mustang nicknamed "Ms. Sally"), and, despite his incoherent ramblings and womanizing, often displays himself to be very intelligent and philosophical. Although hinted at previously, in episode 18 of season 13, his first name is finally revealed when a Canadian woman who lives next door to the family that trades houses with him for the summer calls him "Jeff", and the driver's license shown in the 13th season finale reads "Boomhauer, Jeff". Throughout the series it is never known what he does for a living, although it was revealed in an early episode that he was an electrical engineer, but was on workers' compensation. At the end of the 13th season finale, a badge seen in his open wallet reveals that he is a Texas Ranger. By season 14, Boomhauer is dating a woman who has a son, whom he treats like his own.

Luanne Leanne Platter Kleinschmidt (née Platter) (voiced by Brittany Murphy from 1997 to 2009) is the Hills' 19-year-old niece, daughter of Peggy's scheming fraternal twin brother Hoyt and his alcoholic former wife Leanne. Luanne moves in with the Hills after her mother Leanne stabs Hoyt with a fork during a drunken fight that tips over their trailer. Hank initially makes frequent attempts to encourage Luanne to move out on her own, but later more or less accepts her as a member of the family. She was a student at the beauty academy and later at Arlen Community College. She was often portrayed as an airhead. When Peggy was scammed by an internet test that "proved" she was a genius, she only believed it to be a scam upon learning that Luanne was also proclaimed a genius. Despite this, Luanne was shown to be an expert mechanic in the first two seasons and is good at logic puzzles. She also has something of a vindictive streak, especially when she feels slighted; she was once shown to have tried flushing Hank's keys down the toilet after being passed over for a propane sales position he was hired for instead (though she actually flushed Peggy's by mistake), and later tried putting Peggy's shoes and glasses down the garbage disposal and intentionally dyed Peggy's hair green after being fired as her stylist for a local beauty pageant. Luanne was promiscuous, but she settles down after being visited by the spirit of her first boyfriend, the slacker Buckley, whom she calls "Buckley's angel", and then attending a church-sponsored "born-again virgin" program, where she starts a Bible study class. Luanne created a puppet show entitled "The Manger Babies" for a public-access television cable TV station, featuring the barnyard animals who witnessed Jesus's birth (though they included a penguin and an octopus). In the 10th-season finale, Luanne revealed that she was pregnant with the child of Lucky, whom she married in the 11th-season finale. In the 13th season, she has a baby girl named Gracie Margaret Kleinschmidt. She wears a green sleeveless crop top and red capris (or, in some early episodes, a red-orange T-shirt and blue jeans). Outside of a photograph she does not appear in season 14, as a result of Murphy's death in 2009, nor was she mentioned, leaving her fate unknown.