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:

• Category:20th century in the United States
• 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 present)
• Timeline of the United States