Epigallocatechin gallate (EGCG) is a flavonoid (flavanol) found in Camilla (green tea); it is one of several green tea catechins. EGCG exhibits neuroprotective, antioxidative, anti-inflammatory, anti-diabetic, antifungal, anti-metastatic, and anticancer chemotherapeutic activities. EGCG directly inhibits STAT3 and the aryl hydrocarbon receptor. EGCG inhibits α-synuclein oligomerization in models of Parkinson’s disease and limits amyloid-β (Aβ) aggregation in models of Alzheimer’s disease. In animal models of autoimmune sialadenitis, EGCG inhibits ROS-mediated DNA damage and oxidative stress and increases levels of heme oxygenase 1 (HO-1) and Bcl-2. Additionally, EGCG decreases levels of toll-like receptor 4 (TLR4), IKKβ, activated NF-κB, TNF-α, CD68, and IL-6, suppresses macrophage infiltration, increases levels of PI3K and GLUT4, inhibits α-amylase and α-glucosidase, and improves insulin signaling in animal models of diabetes. In hepatocarcinoma cells, this compound induces S-phase cell cycle arrest and apoptosis and decreases levels of PI3K, Akt, and NF-κB. In other cellular models, EGCG inhibits the epithelial-to-mesenchymal transition (EMT) and limits cell motility; it also indirectly inhibits EGFR. In animal models of bladder cancer, EGCG decreases tumor growth. This compound also induces apoptosis in Candida. EGCG directly inhibits HSP90 in animal models of prostate cancer, decreasing tumor size and progression.