Litigation is inherently linked to the presence of a defendant, typically defined as the individual against whom the main claim is made. However, complexities arise when we encounter "improper defendants"—individuals who lack any substantive connection to the litigation or legal relationship with the plaintiff, yet are included in the defendant list, often to establish jurisdiction based on their residence. The question about such defendants, called "improper defendants," is what is meant by an improper defendant, and by what criteria can the court identify them? Also, what are the motives that lead to the inclusion of an improper defendant in the lawsuit and what solutions are there to counter these motives? The present paper aims to provide a suitable answer to these questions using a descriptive-analytical method, library resources, and extensive study of judicial proceedings. Ultimately, the conclusion is that: 1. An improper defendant is a defendant against whom neither a main nor a minor claim has been filed, nor does it facilitate the handling of the case. 2. Abuse of local jurisdiction and time constraints, prevention of striking out the claim and protest of a third party, as well as acceleration of obtaining evidence are among the motivations for including an improper defendant. To deal with including an improper defendant, there are various solutions such as striking out the claim, issuing cost security orders, along the proper interpretation of relevant procedural rules.