Khan hopes the move will halve harmful nitrogen oxide emissions in central London, where air pollution is thought to cost 9,000 premature deaths per year.
Under the scheme, vehicles will be charged £12.50 ($15.50, 14.60 euros) to enter a planned "ultra-low emissions zone" (ULEZ) around the city centre.
Diesel cars more than four years old in April 2019 and petrol cars more than 13 years old will face the charge 24 hours a day.
Private buses, coaches and trucks failing to meet emissions standards will have to pay £100.
"The air in London is lethal and I will not stand by and do nothing," Khan told AFP.
The ULEZ will have the same boundary as the current congestion charge zone, where vehicles pay £11.50 to enter the city centre between 7:00am and 6:00pm Monday to Friday.
The pollution charge would come on top of the congestion charge.
Khan said he wants to extend the ULEZ to a far wider area of London in 2021.
"One of the big reasons that the air in London is lethal is because of the emissions of vehicles," Khan said.
"We've estimated that more than half of the air pollution is caused by transport.
"It's really important to recognise that poor quality air is one of the reasons why there are 9,000 premature deaths in London each year, more than 40,000 premature deaths across the UK and children having defective lungs, plus adults suffering poor health."
Last week, Khan joined his counterparts from Paris and Seoul to launch an initiative to rate the most polluting vehicles in a bid to keep them off the roads of their cities.
The aim of the "Air'volution" scheme is to help drivers to avoid buying the most harmful diesel vans and cars.
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