This thesis provides a general descriptive account of the morpho-syntactic expression of negation in fifteen Modern Arabic varieties and investigates three of these varieties in more depth. The thesis contributes to the typological literature on negation through a survey of the negation patterns in a number of related and geographically close varieties. It sheds light on the most influential factors that unify the negation patterns found in these varieties, which are predicate type and form. It is found that the type of the predicate, such as verbal and nonverbal predicates, as well as the form of the verbal predicate, such as active participle as opposed to other verbal forms, play an essential role in determining the negation markers used. In addition, this thesis gives a comprehensive account of a number of negative elements in Libyan Arabic, namely the negative auxiliary, negative particle mʕəš, and miš as a metalinguistic marker, and establishes the morpho-syntactic properties and pragmatic functions of these elements. It concludes that the negative auxiliary is used for a specific pragmatic function, which is to deny assumed background information. It also finds that even though miš is not a negation marker exclusive for metalinguistic negation, it is a special metalinguistic marker that signals the metalinguistic reading of verbal sentences.