How old must citizens be to vote in the U.S.?

In the United States, the legal voting age is established by the 26th Amendment to the Constitution, which states that citizens who are 18 years of age or older cannot be denied the right to vote based on age. This amendment was ratified in 1971, lowering the voting age from 21 to 18, reflecting a societal belief that young adults should be eligible to participate in elections, particularly as many of them were being drafted for military service at that age. As a result, 18 years old is the age at which citizens can legally register and vote in elections across the country.