This paper reviewed systematically the odor production and emissions in wastewater systems including sewer and wastewater treatment plants (WWTP). The subjective and objective characterization of wastewater odor was briefly discussed while the recent literature data of the measured concentrations of various odor compounds is collated with their odor description, threshold value, and human health limits. The extensive compiled data provide a full range of spatial and temporal variations. It was found that hydrogen sulfide, organic sulfur compounds, and aldehydes are the key odorants in sewer emissions. The odor emission from different treatment units of a WWTP are distinct from each other. The primary treatment odor is similar to that from the sewer with high level of hydrogen sulfide. In contrast, the odor from sludge handling units are characterized with high organic compounds and very low level of hydrogen sulfide. Odor from both sewer and WWTP are affected by the operation and environmental conditions. Typical diurnal and seasonal pattern can be observed due to the hydraulic patterns. A prioritization framework is proposed to rank the complicated odorants in wastewater emissions for the design and optimization of treatment and control measures.