Focal segmental glomerulosclerosis (FSGS) is a common cause of nephrotic syndrome, accounting for 40% of cases in adults and 20% in children. In FSGS, some glomeruli are sclerosed (focal), with only a portion of each affected glomerulus involved (segmental). FSGS is one of the most prevalent causes of primary glomerulopathy in adults. FSGS can be broadly classified into primary, with no identifiable cause, or secondary. Genetic causes can also be classified either separately or with primary FSGS. Secondary causes of FSGS include infections, certain drugs, hemodynamic maladaptations in the kidney, and genetic factors. Although clinical signs may suggest FSGS, the diagnosis can only be confirmed through histopathological findings. Histologically, FSGS is characterized by segmental scarring that affects part of the glomerulus and involves only a subset of the glomeruli sampled. Recent research has highlighted that the pathogenesis of FSGS involves podocyte injury and damage, which leads to protein loss and the development of focal sclerosing lesions. Categorizing FSGS as primary or secondary has important prognostic and therapeutic implications. The most common clinical manifestation of FSGS, observed in over 70% of patients, is nephrotic syndrome, characterized by generalized or dependent edema, fatigue, and loss of appetite. Hypertension is also common and can be severe, with diastolic blood pressure exceeding 120 mm Hg, particularly in patients of Afro-Caribbean origin.