.45

.45 may refer to:

• .45 ACP, a cartridge designed by John Browning in 1904, for use in his prototype Colt semi-automatic .45 pistol and eventually the M1911 pistol adopted by the United States Army in 1911
• .45-70, a cartridge developed at the U.S. Army's Springfield Armory
• .45 Colt, a handgun cartridge dating to 1872
• .45 (film), an independent 2006 thriller film starring Milla Jovovich, Angus Macfadyen, Aisha Tyler, Stephen Dorff, and Sarah Strange

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