This thesis analyses criminal justice discourse as it relates to offensive language crimes in Australia. Across Australia, and elsewhere, it is a crime to use offensive, indecent or obscene language in or near a public place. These crimes are governed by broadly drafted provisions that allow police and judicial officers significant discretion in determining offensiveness. Although offensive language crimes can theoretically target a multitude of words and phrases, in practice, the laws are used to police and punish a small selection of swear words. Provisions that circumscribe offensive speech have a linguistic dimension. This dimension has been under-theorised in previous scholarship on the topic. Accordingly, my thesis places language at the centre of offensive language crimes, by interrogating how such crimes are represented and legitimised as a particular discursive formation within the criminal justice system. My thesis asks two questions: Firstly, how is offensive language represented in criminal justice discourse? Secondly, how are offensive language crimes legitimised in criminal justice discourse? I employ a distinct approach to these questions by employing critical discourse analysis (‘CDA’) as my primary methodological tool. CDA is not strictly a ‘method’, but rather, a loosely grouped body of work that views language as both shaping and shaped by society. Analysts works from the premise that we cannot neutrally represent reality. Instead, we construct (and reconstruct) reality, including social identities, subject positions, social relationships and systems of knowledge and belief, through language. I use the phrase ‘criminal justice discourse’ to describe socially constructed ways of signifying reality, through language, in the criminal justice system. My thesis situates its linguistic analysis of offensive language crimes in broader social, political and historical contexts. I draw into the frame linguistic research on swearing, and literature relating to metaphors, purity and disgust. The thesis structure is based on the following themes: language interpretation in the courts; swearing, danger and disgust; context; objective standards; and power, order and authority. These themes are derived from my doctrinal analysis of offensive language crimes and ideas that inform and legitimise the criminal punishment of swearing. My thesis reconceptualises how offensive language is interpreted in the criminal law. I extend existing scholarship by highlighting how criminal justice discourse creates and entrenches power inequalities, augments judicial discretion, ignores difference and promotes unfairness. I demonstrate how discourse shapes perceptions about things, people, ideas and words that are deemed ‘out of place’ and worthy of criminal sanction.