G. Madhavan Nair (Malayalam: ജി. മാധവന്‍ നായര്‍) (born October 31, 1943) is the present Chairman of Indian Space Research Organisation and Secretary to the Department of Space, Government of India since September 2003. He is also the Chairman, Space Commission and acts as the Chairman of Governing Body of the Antrix Corporation, Bangalore. Madhavan Nair was awarded the Padma Vibhushan, India's second highest civilian honour, on January 26, 2009.

Nair was born at Neyyattinkara near Thiruvananthapuram, Kerala, India. He also studied as a youth in Kanyakumari District. He graduated with a B.Sc. in Engineering (1966) from College of Engineering, Thiruvananthapuram, Kerala University with specialization in Electrical & Communication Engineering. After his graduation Nair attended a training program at the Bhabha Atomic Research Center (BARC) Training School, Mumbai.

Nair is a leading technologist in the field of rocket systems and has made significant contribution to the development of multi-stage satellite launch vehicles, achieving self-reliance in independent access to space using indigenous technologies. Nair and his team have advanced their work in the face of several challenges in the regime of technology denials by adopting several innovations and novel techniques to realise world class launch vehicle systems. India today has a pride of place amongst the space-faring nations in launch vehicle technology. Specifically, as Project Director, he led the development of Polar Satellite Launch Vehicle (PSLV) which has since become the workhorse for launching mainly Indian remote sensing satellites.