Gamma-Hydroxybutyric acid (GHB) is a CNS depressant that has been abused recreationally for its purported euphoric and relaxation effects and for the purposes of drug facilitated sexual assault due to its sedative and amnesic effects at higher doses. The dramatic increase in the abuse of GHB and association in criminal investigations over the past decade has created the need for forensic laboratories to develop analytical methods to detect GHB in a variety of matrices. The method developed in this work used solid-phase microextraction (SPME) to extract GHB from aqueous samples followed by on-fiber derivatization and analysis by gas chromatography/mass spectrometry (GC/MS). This method detected GHB in aqueous matrices with good sensitivity, high precision, excellent linearity from 0.01 mg/mL to 0.25 mg/mL, and without the need for sample manipulation that could cause interconversion between GHB and its lactone, GBL. The method was successfully applied for detection of GHB in spiked water and beverage samples.