"More Cowbell" is a comedy sketch that aired on Saturday Night Live on April 8, 2000. The sketch was written by regular cast member Will Ferrell and depicts the recording of the song "(Don't Fear) The Reaper" by Blue Öyster Cult. The sketch stars guest host Christopher Walken as fictional music producer Bruce Dickinson, and Ferrell as fictional cowbell player Gene Frenkle, whose overzealous playing annoys his bandmates but pleases Dickinson. The sketch also features Chris Parnell as Eric Bloom, Jimmy Fallon as Bobby Rondinelli, Chris Kattan as Buck Dharma, and Horatio Sanz as Joe Bouchard.

The sketch is one of the most popular SNL sketches ever made; in many "best of" lists of SNL sketches, it places in the top ten (ranked ninth by Rolling Stone, for example). As a result of its popularity, "more cowbell" became an American pop culture catchphrase, and it has even entered the dictionary.

An episode of VH1's Behind the Music documenting the band Blue Öyster Cult showcases footage of the group from a 1976 recording session that produced the band's biggest hit, "(Don't Fear) The Reaper". The producer Bruce Dickinson (played by Christopher Walken) tells the band they have "what appears to be a dynamite sound". The first take seems to go well but the band stops playing because the cowbell part is rather loud and distracting. Dickinson, to the surprise of most of the band, asks for "a little more cowbell" and suggests that the cowbell player, Gene Frenkle (Will Ferrell), "really explore the studio space this time". Frenkle's exuberance in following this advice causes him to bump into his bandmates as he dances around the cramped studio, thrusting his pelvis wildly in all directions, and the band aborts another take.

After the other band members voice their frustrations, Frenkle sheepishly agrees to tone down his performance in the spirit of cooperation. He passive-aggressively plays the cowbell very close to Eric Bloom (Chris Parnell)'s ear and fails to keep time with the rest of the band. The rest of the band expresses frustration with Frenkle, but Dickinson remains focused only on getting more cowbell onto the track. Frenkle makes an impromptu speech to the rest of the band, declaring that Dickinson's stature lends a great deal of weight to his opinion about the cowbell part and that the last time he (Frenkle) checked, they did not have "a whole lot of songs that feature the cowbell" and therefore he would be "doing himself a disservice, and every member of the band" if he "didn't perform the hell out of this". In the end, the band agrees to let Frenkle play the cowbell part his way. The sketch ends with a freeze frame on Frenkle with the superimposed message: "In Memoriam: Gene Frenkle: 1950–2000."

Will Ferrell's idea for the sketch came from hearing "(Don't Fear) The Reaper" over the years: "Every time I heard [the song], I would hear the faint cowbell in the background and wonder, 'What is that guy's life like?'" Ferrell, who had experience writing sketches for himself from his time with The Groundlings, first submitted the sketch for the episode with Norm Macdonald as host, which aired on October 23, 1999. Some sources credited Donnell Campbell as a co-writer, but this was disproven in an interview with Ferrell and a SNL archive of scripts. SNL creator and executive producer Lorne Michaels was unsure about the premise, though the sketch played well among crew at the table read. According to Seth Meyers, who served as head writer several seasons later, the sketch was submitted over seven times before making the show. Early iterations of the sketch used a woodblock, not a cowbell. Ferrell re-wrote the sketch when Christopher Walken was scheduled to host to fit the actor's rhythm.

The actors who appeared in the sketch had trouble keeping straight faces. They found Ferrell's acting, along with Walken's stone-faced performance, so funny that they were all on the verge of corpsing and ruining the sketch several times. On "Take Two", Walken can be seen through the booth glass, laughing, as Ferrell's too-tight shirt rides up, exposing Ferrell's abdomen while he is dancing and playing the cowbell. Even Ferrell at one point can be seen laughing for a moment soon after Jimmy Fallon laughs for the first time in the sketch. According to Ferrell and Michaels, the sketch did not do well in dress rehearsals, and Ferrell had the idea of performing in a smaller shirt in the live sketch. According to Fallon, Ferrell's tighter shirt made him unable to stop laughing, and he had to bite his drumsticks to avoid breaking the scene.

While the song "(Don't Fear) The Reaper" by Blue Öyster Cult does indeed include a cowbell playing throughout, its sound is largely drowned out by the rest of the instruments. According to Donald "Buck Dharma" Roeser, the lead singer and author-composer of the song, the sketch accurately portrays the band's look during the 1970s, but it inaccurately portrays some of the details of the actual recording:

The sketch's offbeat nature, as well as the actors breaking character, made the sketch an immediate fan favorite. Marc Spitz called it "one of the first super-memes of the new century" in The New York Times. Walken continued to hear from fans about the sketch in years afterward: "I hear about it everywhere I go. It's been YEARS, and all anybody brings up is 'COW-bell.' I guess you never know what's gonna click." Ferrell even speculates that it "ruined" Walken's life. Members of Blue Öyster Cult reacted favorably to the sketch. The song's lead vocalist, Buck Dharma, asserted in 2016 that the song had been deemed creepy before "Ferrell pretty much sabotaged that" but that its initial intent "has not only been restored but also seems to be unstoppable".