XS may stand for:

• SITA (IATA airline code)
• Cross-section
• Excess
• "Extra Small", a size of clothing. European clothing-size standard EN 13402 defines the size code XS to refer to chest girths 78–86 cm for men's clothes and bust girths 74–82 cm for women's clothes. Manufacturers also use their own non-standard defining body measurements for this size code.
• A comic book character from DC Comics – see XS (comics)
• XS Energy Drink, a brand name of sugar free energy drinks
• XS (Perl), an interface through which computer programs written in Perl can call C language subroutines
• XS (LISP dialect), A Scheme-like dialect of LISP, for programming LEGO Mindstorms systems
• Xavier School, a Jesuit Catholic college preparatory school with a distinct Chinese and Filipino character
• XS (file sharing), a file sharing hub and client under development by Phoenix Labs

XS