The primary cause of the economic decline known as the Great Depression was the stock market crash of 1929, which severely undermined consumer and investor confidence. The crash was followed by a banking crisis, resulting in the loss of savings and a sharp decline in credit availability. This economic turmoil led to massive unemployment and widespread business failures, as companies could not sustain operations without adequate demand. Other contributing factors included overproduction, reduced consumer spending, and restrictive monetary policies. The Great Depression had profound effects globally, reshaping economic policies and leading to significant government interventions in economies worldwide.