While other Christian figures have recently criticised the Republican over his US travel ban affecting seven Muslim-majority nations and his recognition of Jerusalem as Israel's capital, Mr Graham said he "applauded" Mr Trump.
Speaking to Fox News to mark one year since Mr Trump's inauguration, he said: "President Trump has been defending Christians and I find this refreshing; to have a president who's not afraid to say 'Jesus'.
"He's not afraid to have prayers where people pray in the name of Jesus; we've never had this - not in my lifetime.
"He defends the Christian faith more than any president in my lifetime."
Graham's fresh endorsement came after Donald Trump drew praise from Christian campaigners on Thursday when he announced a new division at the US Department of Health to help ensure hospitals and clinics are respecting the religious beliefs of doctors and nurses.
Franklin Graham also accused left-wing figures of "trying to destory" the US President, adding that Trump has been attacked since "day one" and "we need to pray for this man".
He added: "He's not president perfect; he's got his flaws like we all do but he is certainly trying to fix this nation so it'll be better for my grandchildren and his grandchildren."
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