Consumer Wearable Devices (CWD) enable passive, low-burden, longitudinal collection of data relevant to health behaviors, human performance, and biometrics. Such data are increasingly used to tailor clinical and public health interventions and as outcome measures in clinical trials. The uptake of CWD in research applications warrants an examination of the data collected from these products. This ontology was developed based on a review of publicly available documentation and data sets from three CWD vendors and is open for researchers to modify + extend as new features become available.