XAA

XAA may refer to:

Science

 * Xaa, the abbreviation for an unspecified amino acid
 * Xaa-Pro aminopeptidase, an enzyme
 * Xaa-Xaa-Pro tripeptidyl-peptidase, an enzyme

Other uses

 * ISO 639:xaa, Andalusian Arabic
 * XFree86 Acceleration Architecture, an X Window System driver architecture