The world’s total gold supply varies depending on whether you mean gold already above ground or gold still in the earth: [1, 2]

• Above-Ground Gold (Central Banks & Mined Stock): The world has mined roughly 220,000 tonnesthroughout history. Of this, central banks and official institutions hold approximately 39,000 to 54,000 tonnes as official reserves. [1]
• Below-Ground Reserves: There are an estimated 54,000 to 64,000 tonnes of proven, economically recoverable gold reserves left in the ground. [1, 2, 3]

Top 3 Central Bank Gold Reserves: [1, 2]

• United States: ~8,133 tonnes
• Germany: ~3,350 tonnes
• Italy: ~2,452 tonnes [1, 2]