Cars registered before 2005 will be required to pay an extra £10 for entering the London Congestion Zone from 23 October.
He said the T-charge was the "toughest emission standard of any major city" and was overwhelmingly backed by Londoners because they wanted immediate action to tackle air pollution.
The T-Charge, which could impact up to 10,000 vehicles that are failing to meet Euro 4 standards, is the latest weapon in the Mayor's arsenal to combat air pollution.
Days after the European Commission issued a "final warning" to Britain and four other countries to address breaches of nitrogen dioxide pollution limits, London mayor Sadiq Khan on Friday announced a new £10 charge to deal with the crisis in the metropolis.
In total, more than 37 stakeholders and organisations - including numerous councils, Global Action Plan and the Licensed Taxi Drivers Association - support the principle of the T-Charge, which uses cameras as monitoring and enforcement measures.
The news follows Westminster Council's announcement in January that drivers of diesel cars will pay 50% extra to park on the streets surrounding Marylebone from April, as well as proposals for a London-wide scrappage scheme for older diesel cars. But the latest research shows that these diesel vehicles are now responsible for nearly 40% of all NO2 emissions in the UK's major cities.
Dr Penny Woods, chief executive of the British Lung Foundation, called the charge an important step to deter the most polluting and harmful vehicles from entering Central London.
Khan also urged the government to help motorists move away from diesel vehicles and ratify a "Clean Air Act for the 21st century".
The Toxicity Charge will cost £10 and applies to the same areas and times covered by the London Congestion Charge; it will also operate using the same payment systems.
These include no longer buying diesel buses, doubling the amount invested in retrofit buses, and the introduction of an Ultra Low Emission Zone from 2018.
"I will continue to do everything in my power to help protect the health of Londoners and clean our filthy air". We are pleased the Mayor has prioritised improving air quality.