The classical Hindustani vocalist Pandit Omkarnath Thakur belonged to the state of:

Gujarat
Rajasthan
Uttar Pradesh
Maharashtra

The correct answer is: Uttar Pradesh.

Pandit Omkarnath Thakur was born in 1897 in the town of Jaunpur, Uttar Pradesh. He was a renowned classical Hindustani vocalist and is considered one of the greatest singers of the 20th century. He was a disciple of Ustad Alladiya Khan and was known for his mastery of the khayal style of singing. He also composed several ragas and was a pioneer in the field of Hindustani music education.

Gujarat is a state in western India. It is the fifth-largest state in India by area and the ninth-most populous state. The capital of Gujarat is Gandhinagar. The state is home to a number of different cultures and languages, including Gujarati, Hindi, and Marathi.

Rajasthan is a state in northwestern India. It is the largest state in India by area and the second-most populous state. The capital of Rajasthan is Jaipur. The state is home to a number of different cultures and languages, including Rajasthani, Hindi, and Punjabi.

Uttar Pradesh is a state in northern India. It is the most populous state in India and the second-largest state by area. The capital of Uttar Pradesh is Lucknow. The state is home to a number of different cultures and languages, including Hindi, Urdu, and Punjabi.

Maharashtra is a state in western India. It is the third-largest state in India by area and the third-most populous state. The capital of Maharashtra is Mumbai. The state is home to a number of different cultures and languages, including Marathi, Hindi, and Kannada.