Australian athlete Daniel Batman has been killed in a car crash south-east of Darwin.

Police say Batman, 31, who lived in Canberra, was travelling east towards Kakadu on the Arnhem Highway sometime after midnight when his vehicle veered off the road and rolled 10 metres.

Senior Constable Allan Macdonald says officers are still investigating the accident, but they say speed and alcohol are probably to blame.

"For some unknown reason he's lost control at the curve and continued on behind me where the car's ended up," he said.

"It appears he's hit a culvert back over near where the sign is there off the actual road and unfortunately that looks like what's flipped the car."

Batman was a sprinter, competing in the 100m, 200m and 400m. He also competed at the 2000 Sydney Olympics.

He was the national men's 200m champion in 2005 and 2006.

His greatest achievement on the world stage was sixth place at the 2003 World Indoor Championships.

Batman had two children with former sprinter and Australian hockey player Nova Peris-Kneebone.

He has another child with his partner, Natalie Sainsbury. Liberty was born last year.

He was also a direct descendant of John Batman, the founder of Melbourne.