This chapter provides an in-depth exploration of research design, serving as the foundational blueprint for conducting robust and systematic research. It begins with a detailed definition of research design and its pivotal role in ensuring the validity, reliability, and generalizability of findings. The chapter categorizes research methodologies into qualitative, quantitative, and mixed-methods approaches, elucidating their characteristics, strengths, and limitations. Specific focus is given to various observational, experimental, and descriptive study designs, including cross-sectional studies, case-control studies, cohort studies, and ecological studies, with practical examples to illustrate their applications in public health. Furthermore, the chapter underscores the critical importance of choosing the appropriate research design based on the study’s objectives, ensuring the alignment of methodology with intended outcomes. This systematic overview equips researchers with the tools to effectively plan and execute studies that contribute meaningful insights across disciplines.