The last two races of the season will be at London's ExCel Centre on July 29th and 30th, with Dennis now 24 points clear of Envision Racing's New Zealander Nick Cassidy (28) at the top of the standings.
The points difference means Dennis, who also took fastest lap on Sunday, could clinch the title with a race to spare.
Cassidy, who retook the championship lead on Saturday when he finished second on the streets of Rome's EUR district, finished 14th on a hot Sunday after being hit from behind by compatriot and rival Mitch Evans (29) on lap two.
Jaguar's Evans, winner on Saturday, retired.
French driver Norman Nato (31) was second for Nissan, despite a broken front wing, with Britain's Sam Bird (36) third for Jaguar.
Dennis led every lap from pole position on Sunday and now has 195 points to Cassidy's 171 with Evans on 151, while Porsche's Pascal Wehrlein (28) is fourth overall and on 146 points.
Envision lead the team standings with 253 points to Porsche's 239 and Jaguar on 228.
"Now we have a home race in London, we are big there," said Dennis, who took a first and second from the two London races last year as well as winning in 2021.
"We are going to try and do the business there but I am going to enjoy this for now," added Dennis.
Dennis led from the start with Cassidy chasing before Evans locked up and hit the back of his compatriot's car with the Jaguar launched into the air and the safety car deployed.
"I wanted to make progress and position myself into turn eight to get Nick but obviously it didn't go to plan," said an apologetic Evans.
"I feel sorry for Nick, and the Envision Racing guys. This has obviously really hurt my championship now."
