The main cause of the fall of the Roman Empire is a complex combination of internal weaknesses and external pressures. Among the most significant factors were political instability, economic troubles, and military challenges. Frequent changes in leadership led to a lack of effective governance, while economic decline resulted from heavy taxation and reliance on slave labor. Externally, invasions by barbarian tribes such as the Visigoths and Vandals contributed significantly to the empire's decline. The culmination of these issues, coupled with social decay and the rise of Christianity, ultimately led to the collapse of the Western Roman Empire in the late 5th century.