The FBI has updated its definition of rape for the first time in 83 years, to include men and those who do not physically resist as victims.
The new definition will increase the number of people counted as rape victims in FBI statistics, but it will not change federal or state laws.
Lawmakers use those statistics to allocate resources for prevention and victim assistance.
Many US states have already adopted a wider definition of rape.
Previously, the FBI defined the crime of rape as "the carnal knowledge of a female, forcibly and against her will".
The new definition removes the reference to females and says rape is "the penetration, no matter how slight, of the vagina or anus with any body part or object" without the consent of the victim.
Also specified is "oral penetration by a sex organ of another person" without consent.
Vice-President Joe Biden, who raised the issue last July at a Cabinet meeting, called the change a victory for those "whose suffering has gone unaccounted for over 80 years".
"We can't solve it unless we know the full extent of it," Mr Biden said.
One in five women and one in 71 men have been raped at some point in the lives, according to a 2010 study by the Centers for Disease Control , which used a broader definition.
The US Congress approved $592m (£384m) this year to address violence against women.
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