The 24-year-old — who recently won the Tour Down Under — broke the previous mark of 51.852 kilometres set by Austrian Mathias Brandle last October in Aigle, Switzerland.
Dennis, world track pursuit champion in 2011, was always on target to break the record and was at one point in line for completing 52.739 kilometres but he slowed down in the final ten minutes.
His success, at a track close to his team BMC's headquarters, comes a week after his compatriot Jack Bobridge failed in his bid in Melbourne.
"I feel pretty proud, also happy," Dennis said.
"I've prepared myself for a long time, it's a huge relief," he said.
"I'm really proud to take the chance. 2015 starts better than expected, with the victory in the Tour Down Under and now this record," Dennis said.
"It's absolutely amazing," he said.
"We set 52.5 kilometres as the goal, above this it would have been a bonus."
Dennis said that he believed he could improve on the record.
"Yes I can improve this record," he said.
"There are some things I didn't do perfectly, my pacing could be better, I could have more control.
"As I'm getting older, I'm getting stronger."
Dennis, Olympic team pursuit silver medalist in 2012, may not have the record for long as several other formidable cyclists have pledged to tackle the mark this year including British legend Olympic and world time-trial champion as well as the 2012 Tour de France winner Bradley Wiggins.
"Wiggins is the main rider to be able to beat me," admitted Dennis.
"There's also (Thomas) Dekker, we have to see what the altitude in Mexico can bring."