Kidney diseases are a global health problem, and their frequency is continuously increasing. Available treatments provide limited kidney protection. The protective effect of the green tea polyphenol epigallocatechin-3-gallate (EGCG) in several diseases have been extensively investigated. Experimental and clinical studies have shown that the antioxidant, anti-inflammatory, and anti-apoptotic properties of EGCG are promising for the treatment and/or prevention of kidney diseases. This review analyzes the available evidence on the effects, and the likely protective mechanisms of action, of EGCG in a broad spectrum of kidney diseases, including acute kidney injury, drug-induced nephrotoxicity, kidney stone disease, diabetic nephropathy, chronic kidney disease, and kidney fibrosis.