What is the age requirement to become President of the U.S.?
Under the U.S. Constitution, the President of the U.S. must be at least thirty five (35) years old. Historians note that 35 was "older" when the U.S. Constitution was written. The average life expectancy in the 1700s was much lower than it is today. When the Constitution was written, life expectancy was about 40 years. However, this was a misleading average. It took into account many people who died at birth or in early childhood. The Founding Father and first president of America, George Washington, lived to the age of 67. Thomas Jefferson (the third president) died at 83.
See the U.S. Constitution, Article II Section 1 Clause 5.