Who defeated the Gupta dynasty?

The Gupta dynasty was defeated by the invading White Huns, otherwise known as the Hephthalites. Although the dynasty was not completely destroyed, the White Huns caused considerable damage to the empire, leading to its decline.

For further reading check the following articles:

• Harshavardhana – Facts about the King Harsha
• Gupta Empire
• Pallava Dynasty