As per Census 2011, the most populous district of Bihar is

As per Census 2011, the most populous district of Bihar is Patna. It has a population of 53,51,816. The other options are incorrect.

• Madhubani has a population of 4,533,814.
• Saran has a population of 4,199,691.
• Gaya has a population of 4,006,678.

Patna is the capital of Bihar and the most populous city in the state. It is located on the banks of the Ganges River. Patna is a major center of education, culture, and commerce. It is also home to many historical monuments, including the Patna Sahib Gurudwara, the Golghar, and the Patna Fort.