The first inauguration of Harry S. Truman as the 33rd president of the United States was held at 7:09 pm on Thursday, April 12, 1945, at the Cabinet Room inside the White House in Washington, D.C., following the death of President Franklin D. Roosevelt earlier that day.

Truman, then serving as vice president of the United States, had just adjourned a session of the United States Senate and was on his way to share a drink with Sam Rayburn, the speaker of the House of Representatives, when he was summoned to the White House.

"[1] Chief Justice of the United States Harlan F. Stone administered the presidential oath of office;[2] Stone began the oath "Do you, Harry Shipp Truman..." in the erroneous belief that Shipp was the President's mother's maiden name and, by extension, his middle name,[3] to which Truman replied, "I Harry S. Truman..."[4] before the oath was continued.

At the end of the ceremony, which lasted about a minute, Truman kissed the Bible.

[7] The next morning Truman told a group of reporters “There have been few men in all history the equal of the man into whose shoes I am stepping, I pray God I can measure up to the task.