Who is the Chairman of the National Development Council?

Prime Minister of India

The Planning Commission was set up in March 1950 by a simple resolution of the Government of India.
The Prime Minister was its Chairperson.
It was an extra-constitutional and non-statutory body.
It became the most influential & central machinery for deciding what path & strategy India would adopt for its development.
It had an advisory role and its recommendations became effective only when the Union Cabinet approved these.

The Government of India replaced the Planning Commission with a new institution named NITI Aayog.
NITI Aayog stands for National Institution for Transforming India.
The NITI Aayog came into existence on 1 January 2015.