Step 1: Religious significance in Vijayanagara.
The rulers of the Vijayanagara Empire gave great importance to divine patronage. Every dynasty had a presiding deity or mother goddess they worshipped.
Step 2: Identification of Pampadevi.
In the case of Vijayanagara, Pampadevi, a form of Goddess Parvati associated with the Tungabhadra River and Hampi region, was worshipped as the mother goddess. The city itself was originally called “Pampakshetra” in her honor.
Step 3: Conclusion.
Thus, the mother goddess of Vijayanagara was Pampadevi.
\[
\boxed{\text{Pampadevi}}
\]