When Babur invaded India, the ruler of the Vijayanagar Empire in South India was Krishnadevaraya.

Background:
The Vijayanagar Empire, also known as the Kingdom of Bisnagar, was a prominent Hindu empire that ruled over South India from the 14th to the 17th century. The empire reached its peak during the reign of Krishnadevaraya, who was known for his military prowess, administrative skills, and patronage of arts and culture.

Babur's Invasion:
In 1526, Babur, the founder of the Mughal Empire, invaded India. He defeated the last Sultan of Delhi, Ibrahim Lodi, in the First Battle of Panipat and established Mughal rule in Northern India. After consolidating his position in the north, Babur set his sights on expanding his empire further south.

Ruler of Vijayanagar Empire:
During Babur's invasion of India, Krishnadevaraya was the ruler of the Vijayanagar Empire. He ascended to the throne in 1509 and ruled until his death in 1529. Krishnadevaraya was one of the most prominent kings of the Vijayanagar Empire and is often referred to as its greatest ruler.

Accomplishments of Krishnadevaraya:
Under Krishnadevaraya's rule, the Vijayanagar Empire experienced a period of prosperity and cultural advancement. He was a capable administrator and implemented various reforms to improve governance and strengthen the empire. Krishnadevaraya also expanded the empire's territory through military campaigns and strategic alliances.

Patronage of Arts and Literature:
Krishnadevaraya was a great patron of arts and literature. He himself was a scholar and composed several works in Telugu and Sanskrit. The Vijayanagar Empire witnessed a flourishing of literature, music, dance, and architecture during his reign. Many notable poets, scholars, and artists thrived under his patronage.

Conclusion:
In summary, when Babur invaded India, the ruler of the Vijayanagar Empire in South India was Krishnadevaraya. He was a capable and renowned king who contributed significantly to the empire's prosperity and cultural development. Krishnadevaraya's reign marked a golden era in the history of the Vijayanagar Empire.