Strong Bad is a fictional character from Homestar Runner, a animated Flash web series, who is inspired by "The Strong Bads" from the video game Tag Team Wrestling. He is voiced by Matt Chapman, the principal voice actor and co-creator of the series. Strong Bad enjoys pranking the other characters of the series, along with his ever-diligent lackey pet The Cheat and his older brother Strong Mad. Strong Bad first became popular due to his own segment on the Homestar Runner website, called "Strong Bad Emails". The Strong Bad Email series grew to be so popular that six DVDs featuring the emails have been released, as well as a podcast where emails could be downloaded to digital media players, since its first episode in 2001.

Strong Bad was created to be the main antagonist of the series but since then has become less of a villain and more of an antihero. However, he is still occasionally referred to as an antagonist, due to the pranks that he, Strong Mad, and The Cheat play on the other characters, and his insulting of his brother Strong Sad. He seems to be a character influenced by the American popular culture trends of the 1970s, 1980s, and 1990s, such as heavy metal music and the second and third-generations of video games and video game consoles. Since he is one of the site's most popular characters, merchandise has also spun off Strong Bad, which includes T-shirts and sweatshirts sold by the website.

Strong Bad has been one of the most popular characters in the series and has been well-received. In 2021, Polygon declared Strong Bad an icon. In a tribute, they note that "Strong Bad Email was far and away the most popular segment on Homestar Runner" and the series and character have "remained a "massive comedic influence" on others. Segments have been spun off his emails, including "Teen Girl Squad", a comic drawn by Strong Bad about four teenage friends, and "20X6", an anime-style cartoon featuring Japanese versions of the characters, such as Strong Bad's counterpart, "Stinkoman".

In the original The Homestar Runner Enters the Strongest Man in the World Contest book, as well as many of the early cartoons, Strong Bad mainly served as the antagonist to Homestar Runner. The two would frequently compete against each other in competitions, with Strong Bad often cheating. As the series drew away from competition-based stories and became more character-driven, Strong Bad became less of a villain; although he still dislikes Homestar and often tries to prank him, he mostly just views him as dim-witted and irritating. The two have been known to occasionally get along, however.

Along with his physically intimidating but mentally limited big brother Strong Mad and his yellow lackey The Cheat, Strong Bad represents the self-proclaimed criminal element in the series. Many shorts concern the various practical jokes and scams that they perpetrate. Although these are usually only slightly malevolent, Strong Bad still acts as if he is a villainous mastermind, and he is highly prone to exaggerating his alluring qualities—especially with regards to women. Strong Bad also "rules" an area of the fictional universe called Strong Badia. It consists of a barren field, a fence, a tire, and a stop sign reading "Pop: Tire" (Pop meaning population) leaning against a cinder block. Besides Strong Badia, he and The Cheat enjoy hanging out at a stick known as "The Stick".

Strong Bad's main role in the cartoon is in the Strong Bad Email segment, in which he answers emails sent to him from viewers. The Strong Bad Emails began as a small segment in 2001, in which Strong Bad would mock the spelling and grammar of those who wrote to him, usually while typing with boxing gloves on an outdated computer. The question of how he types with boxing gloves on has become a running gag due to the frequency of emails concerning it, and seems to annoy Strong Bad. Most of the time a cut-away sequence is used to move the narrative beyond mere typing. Once the events of the email finish unfolding, Strong Bad wraps it up, and then "The Paper" or "New Paper" comes down with a link to Strong Bad's e-mail address. Often, hidden animations (Easter eggs) are displayed when the user clicks on a word or picture either during the email or after it has concluded. As of 2022, there are 209 Strong Bad emails. Although the animations were initially brief, they gradually grew to establish numerous catchphrases and running gags. His most used catchphrase was "Holy Crap!" and other variations on this theme (example: "What the crap?"), though he now parodies even this in his responses to emails.

Trogdor the Burninator is an original character created by Strong Bad in the 58th Strong Bad Email, titled "dragon". The cartoon features Strong Bad giving an Ed Emberley-inspired drawing tutorial to the viewer, illustrating a fire-breathing serpent with incongruous details including stick-figure feet and a single, large muscular arm. His fire-breathing destruction is referred to with the term "burnination".

The Trogdor character became very popular, with merchandise featuring the dragon consistently being the best-selling in the store. Trogdor was featured on several games on the website, and accompanied by a memorable song in his first appearance. He featured as the main antagonist of the final episode of Strong Bad's Cool Game for Attractive People, "8-Bit is Enough". In 2018, board game Trogdor!! The Board Game was funded via a Kickstarter campaign.