We report on the development, characterization, and field deployment of a fast time response sensor for measuring ozone (O<sub>3</sub>) and nitrogen dioxide (NO<sub>2</sub>) concentrations utilizing chemical ionization time-of-flight mass spectrometry (CI-ToFMS) with oxygen anion (O<sub>2</sub><sup>−</sup>) reagent ion chemistry. We demonstrate that the oxygen anion chemical ionization mass spectrometer (Ox-CIMS) is highly sensitive to both O<sub>3</sub> (180 ions s<sup>−1</sup> pptv<sup>−1</sup> pptv<sup>−1</sup>) and NO<sub>2</sub> (97 ions s<sup>−1</sup> pptv<sup>−1</sup>), corresponding to detection limits (3σ, 1 s averages) of 13 and 9.9 pptv, respectively. In both cases, the detection threshold is limited by the magnitude and variability in the background determination. The short-term precision (1 s averages) is better than 0.3% at 10 ppbv O<sub>3</sub> and 4% at 10 pptv NO<sub>2</sub>. We demonstrate that the sensitivity of the O<sub>3</sub> measurement to fluctuations in ambient water vapor and carbon dioxide is negligible for typical conditions encountered in the troposphere. The application of the Ox-CIMS to the measurement of O<sub>3</sub> vertical fluxes over the coastal ocean, via eddy covariance (EC), was tested during summer 2018 at Scripps Pier, La Jolla CA. The observed mean ozone deposition velocity (vd(O<sub>3</sub>)) was 0.011 cm s<sup>−1</sup> pptv<sup>−1</sup> with a campaign ensemble limit of detection (LOD) of 0.0042 cm s<sup>−1</sup> pptv<sup>−1</sup> at the 95% confidence level, from each 27-minute sampling period LOD. The campaign mean and one standard deviation range of O<sub>3</sub> mixing ratios were 38.9 ± 12.3 ppbv. Several fast ozone titration events from local NO emissions were sampled where unit conversion of O<sub>3</sub> to NO<sub>2</sub> was observed, highlighting instrument utility as a total odd oxygen (Ox = O<sub>3</sub> + NO<sub>2</sub>) sensor. The demonstrated precision, sensitivity, and time resolution of this instrument highlight its potential for direct measurements of O<sub>3</sub> ocean–atmosphere and biosphere–atmosphere exchange from both stationary and mobile sampling platforms.