Major depressive disorder (MDD), with its heterogeneous nature and variable course, poses significant challenges for clinicians in treatment planning and clinical decision-making. These challenges are further compounded by the rapid emergence of new treatment options and the uncertainty regarding their place within clinical algorithms. In this context, structured treatment guidelines that offer sequential, evidence-based recommendations based on comparative evaluation of available interventions have become essential reference tools for clinicians. Although various international guidelines offer comprehensive recommendations, the absence of a locally relevant and up-to-date guideline tailored to national clinical needs remains a critical gap. This guideline was developed to address that gap, aiming to provide a scientifically grounded and clinically applicable resource for the treatment of depression in Türkiye. This guideline reviews recent developments in MDD treatment and presents evidence-based, sequential recommendations applicable to clinical practice in Türkiye. It also systematically covers assessment tools, clinical subtypes, outcome measures and decision-making processes that may guide treatment planning. This article introduces the methodological framework, development process and the core concepts and definitions related to the guideline.