Smack may refer to the following:

• Smack Apparel, t-shirt company famous for creating t-shirts talking smack against its rivals "getSMACK.com"
• Simplified Mandatory Access Control Kernel, a Linux kernel security module
• Spank or slap, to strike with an open palm
• Smack (library), an open-source library for XMPP messaging
• Smack (Finnish band), a Finnish 80's rock'n roll band
• Smack (American band), an American rock'n roll band
• Honey Smacks, a cereal made by Kellogg's
• Smack (ship), a small decked or half-decked vessel, sailing under various rigs and used principally for fishing
• Smack (nightclub), a world renowned club in Leamington Spa
• Heroin, a drug often known by the street name smack
• Trash-talk, often referred to in the United States as "talking smack"
• Jim Rome, whose sports commentary is often referred to as smack
• A group of jellyfish
• Junk (novel), a 1996 novel by Melvin Burgess, known originally as Junk but published in US as Smack