Observational study designs are extensively used in epidemiology. The appropriate study design to respond to the research question is crucial to the success of a study. The current chapter examines different types of observational study designs and their application in suicide research. Considera-tions about their suitability with regard to their nature, including strengths and limitations, time to implement, budget, and other practicalities for a researcher, study team, and stakeholders are of ut-most importance and are discussed with examples from suicide research. Also discussed are cau-sation and internal and external validity.