Foreign Secretary William Hague and former US Secretary of State Condoleezza Rice will attend the US Embassy in London to reveal the 10-foot bronze figure.
Ms Rice is representing the late president's widow Nancy Reagan at the ceremony, which coincides with the US Independence Day celebrations.
He joins the ranks of great men and women whose statues adorn our London streets; Nelson, Wellington, Lincoln, Churchill, Roosevelt, Edith Cavell and Nelson Mandela.
Mr Hague said: "As a Briton, as a Conservative and as a passionate admirer of America, I am proud that we have made a home here in the centre of our city for President Ronald Reagan.
"Statues bring us to face to face with our heroes long after they are gone.
"Ronald Reagan is without question a great American hero; one of America’s finest sons, and a giant of 20th Century history. You may be sure that the people of London will take this statue to their hearts."
Mr Hague said Baroness Thatcher could not be at the unveiling because of ill health. But he read out the speech she would have made.
"Ronald Reagan was a great President and a great man - a true leader for our times," wrote Baroness Thatcher.
"He held clear principles and acted upon them with purpose. Through his strength and his conviction he brought millions of people to freedom as the Iron Curtain finally came down. It was a pleasure to be his colleague and his friend and I hope that this statue will be a reminder to future generations of the debt we owe him.” ...