The following is a list of episodes from the third season of King of the Hill, which originally aired on Fox from September 20, 1998 to May 16, 1999 for 25 episodes.^[1][2] The season's premiere was preceded by a sneak preview on Fox during August 23, 1998. The Region 1 DVD was released on December 28, 2004. The Region 2 and 4 DVDs were respectively released on August 28 and September 26, 2006.

The showrunners for the season were Greg Daniels and Richard Appel.^[3] This was the first season where Appel was a showrunner, with the first two seasons having been jointly run by Daniels and Mike Judge (who in 1998 was busy directing the film Office Space). Like Daniels, Appel had previously written for The Simpsons. He left that show to join King of the Hill in late 1997, although episodes he had worked on for The Simpsons continued to be aired into 1998. Daniels sought to bring Appel to the show not only because of his previous experience working with him on The Simpsons, but also because he was a close friend who he'd been collaborating with since the 1980s, during his days as a writer for The Harvard Lampoon. In a December 1998 Chicago Tribune article, Daniels said, "It was essential that Rich was a good writer who could deal with people, who could help manage the business in the room. But equally important was the fact that he was someone I could trust, who had a similar sense of taste and values."^[4] In this same article, Appel reflected, "when I first came here, up on the board, they had exercises, and one was a poll with questions like, 'Did Hank and Peggy have sex before they got married?' Then there'd be a tally of what percentage of the writers thought yes. There were 50 questions like that, and it was really interesting. That first season, they spent days and days thinking of backstory for each character, which they could then draw on over the course of the year. It might be something as small as the fact that Peggy has big feet, and she's ashamed of that. But it helps flavor the characters for the writers, and gives a better sense of what they're like."^[4]

The episode "To Spank, with Love" was extensively rewritten after the table read. In the rewritten version, Peggy gets fired after spanking a student in her class; in the original script, the school board instead turned out to be so conservative that they commended Peggy for spanking. After this, there was a montage of Peggy spanking children and she became obsessed with violence.^[5]

King of the Hill was moved to a Tuesday night time slot this season. This led to a decline in ratings, in part due to competition from WB's hit Buffy the Vampire Slayer (which featured Sarah Michelle Gellar, a guest voice for this season). Fox later moved the show back to its original Sunday night time slot.^[3]

In his October 1998 review of the episode "Peggy's Headache", Steve Johnson of the Chicago Tribune wrote, "when it comes to spotting the subtle shadings of human behavior, there is little on TV with so keen an eye as King of the Hill." Johnson added that, "sometimes the characters in cartoons are more human than so-called 'real' actors."^[6] Ken Tucker of Entertainment Weekly wrote in April 1999 that, "when King debuted in 1997, it was a pleasant surprise: Who knew Mike Judge, progenitor of Uberlouts Beavis and Butt-Head, had it in him to create such a subtle, detailed portrait of contemporary middle-class life? This season, the show’s only gotten better — deeper, richer, more true to its guiding intention of presenting people with Texas twangs as something other than the media cliche of rubes with bad taste."^[7] In his December 2004 review of the DVD release, Colin Jacobson of DVD Movie Guide wrote that, "the year suffered from very few flat episodes and offered a lot of strong ones." Jacobson labelled "Pretty, Pretty Dresses" as "one of the darker episodes [focusing] on the less jolly side of the holidays", noting that "this doesn’t exactly make the show a laugh riot, but it’s an interesting take on the subject, especially as Bill goes more and more nuts."^[8]

The Region 1 DVD for the season was released on December 28, 2004, with this release being the first to contain double-sided disks (which would continue through to the sixth season DVD release) and no extras (which would continue for all other DVD releases). The lack of extras was since the show's producers found it difficult to find the time to create worthwhile extras while the show was still on the air. In January 2005, it was reported that they were planning on having special features for future releases, although this never came to fruition. In Region 2 and Region 4, the Season 3 set was released in 2006, and did not utilize double-sided disks.

The episodes are presented in their airdate order rather than in their production order. This slightly disrupts the show's continuity, as Luanne gradually regrew her hair throughout the season following the explosion at Mega-Lo Mart at the end of Season 2.