A unique cloud has been compared to the a nuclear mushroom cloud and the Starship Enterprise after it was photographed hanging above the nation's capital.

The cloud was spotted in the sky from multiple suburbs across Canberra at 2:30pm on Tuesday, February 16 before images were uploaded to social media.

Chris Chia said the sight of the cloud caused motorists to slow down as he drove home to Tuggeranong in the city's southwest.