He made the announcement at an energy conference in Pittsburgh on a stage flanked by men in hard hats.
He described the accord as a bad deal and said his pro-fossil fuel policies had made the US an energy superpower.
The earliest he can formally start the process of withdrawing the US from the Paris accord is 4 November.
The pull-out will take effect a year later - the day after the 2020 US presidential election - assuming that Mr Trump is re-elected.
The Paris agreement brought together 195 nations in the battle to combat climate change.
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