The introduction of a research article is an important area of study, as writers need to cohesively state the significance and current status of research, identify and define the gap, and clearly show how this gap is addressed. To write cohesive research article introductions, writers need to keep track of several linguistic features, among which is the theme. Thus, this study aims to investigate the types, frequencies, and communicative purposes of the marked theme in research article introductions across four disciplines. To this end, a corpus of 40 research article introduction sections from four disciplines—namely applied linguistics, psychology, chemistry, and environmental engineering—was randomly selected to meet the aims of this study. The research article introductions were extracted from articles published in the 2020–2023 issues of international high-impact journals. The corpus was analyzed based on Ebrahimi's (2014) taxonomy of marked themes. The findings suggested that most of the marked theme types were realized frequently in different manners, indicating disciplinary differences. The findings reported that the communicative purposes of marked themes were influenced and guided by the rhetorical functions of research article introductions and the disciplinary conventions of writing. The findings of this study could be included in EAP writing courses, highlighting the relationship between the rhetorical functions of research article introductions and the disciplinary conventions of writing on one end and the conscious use of marked theme types on the other end.