Kirk, a Republican activist, was fatally shot on Wednesday afternoon while hosting an event at Utah Valley University.
In announcing the honor, Trump said: “Charlie was a giant of his generation, a champion of liberty, and an inspiration to millions and millions of people.”
Kirk, aged 31, was the founder of Turning Point USA, a non-profit dedicated to instilling conservative values in young people.
He was a prominent figure in the Republican Party and had fostered a close relationship with Trump.