Wet gas typically refers to a gaseous fluid that contains an amount of liquid. The gas is made up of hydrocarbons while the liquid is usually made up of water, hydrocarbons, or a mixture of both. Wet gas is common in the Oil & Gas Industry, but there is currently no compilation of its effects on machinery. Instead, the available literature on the topic provides many investigations that each have a narrow focus on specific applications. Therefore, it is difficult to understand what is known about wet gas effects on gas machinery. A thorough review of the available literature among different wet gas applications is given in this report to provide an understanding of the current level of knowledge on wet gas operation. Topics include the effects of wet gas fuel on combustion and wet process gas on compressor operation and durability (i.e. erosion, corrosion). Specific compressor types that are reviewed are screw-type, reciprocating, and centrifugal. In addition to machinery, a review of gas-liquid separation is provided along with currently available wet gas test facilities that have been used for research or technology qualification. From the review, the current knowledge gaps are identified and used to suggest topics for future research. It is expected that the Oil & Gas Industry will benefit from this work by having a clear picture of the current knowledge of the effects of wet gas on a range of machinery used in the Industry. The gaps in knowledge are identified among a range of oil and gas applications to provide the Industry with a starting point for future wet gas research. By covering a range of applications, this work reduces the risk of overlap in future wet gas research.