Who is the ex - officio Chairman of the Rajya Sabha? How is he elected?

Rajya Sabha members are elected for 6 years.

The Deputy Chairman is also elected by the House from its members.

The Vice President of India is the ex - officio Chairman of the Rajya Sabha.

Shri M. Venkaiah Naidu is the  ex - officio Chairman of the Rajya Sabha

Hence, the Vice President of India is the ex - officio Chairman of the Rajya Sabha.