More than half a million people commute into the City every weekday and the authorities have already started working to reduce air pollution in the area.
The current speed limit in the City is 20 mph for roads controlled by the corporation, while some larger roads have a 30 mph limit.
The 15 mph limit could go into effect as soon as 2021.
“These radical plans will ensure the continued success of not just the City, but wider London and the UK as a leading global business and cultural destination,” said Alastair Moss, chair of the corporation’s transport and planning committee.