The 20th century in the United States refers to the period in the United States from 1901 through 2000 in the Gregorian calendar. For information on this period, see:

• History of the United States series:
  • History of the United States (1865–1918)
  • History of the United States (1918–1945)
  • History of the United States (1945–1964)
  • History of the United States (1964–1980)
  • History of the United States (1980–1991)
  • History of the United States (1991–2008)
• Historical eras:
  • Progressive Era
  • United States in World War I
  • Roaring Twenties
  • Great Depression in the United States
  • United States in World War II
  • Cold War
  • Civil rights era
  • Reagan era