Sydney will host the world's biggest gathering of space scientists in 2020, at the start of the decade when humans are planning to travel to Mars.

Dubbed the "Space Olympics", the world assembly of the Committee on Space Research, or COSPAR, will convene in Sydney's new billion-dollar convention centre in Darling Harbour.

"This is a ringing endorsement of our people, infrastructure and high regard in the global space community," Science Minister Greg Hunt said.

The successful bid defeated a field of cities including Shanghai, Valencia, Prague and Lausanne.