Senator Martha McSally, who was the first female US fighter pilot to fly in combat, was speaking at a hearing on the sex assaults in the military.
The Arizona Republican said she did not report the rape as she felt ashamed and confused and distrusted the system.
Reports of sexual assaults across the US military jumped nearly 10% in 2017.
Ms McSally told the Senate Armed Services subcommittee on Wednesday: “I stayed silent for many years.
“But later in my career, as the military grappled with the scandals and their wholly inadequate responses, I felt the need to let some people know, I too was a survivor.
“I was horrified at how my attempt to share generally my experiences was handled.
“I almost separated from the Air Force at 18 years of service over my despair. Like many victims, I felt like the system was raping me all over again.”
Senator Kristen Gillibrand of New York, the top-ranking Democrat on the committee, said she was “deeply affected by that testimony”.
Ms McSally served 26 years in the US Air Force, rising to the rank of colonel, before retiring in 2010.
She served two terms in the US House of Representatives before being elected to Senate last year.
It is not the first time Ms McSally has spoken about being a survivor of sexual abuse.
Last year, while running for the Senate, she told the Wall Street Journal her high school athletic coach had pressured her into having sex with him when she was 17.
She has previously said she was sexually harassed while in the military.
In January, another female senator said she had been raped.
Joni Ernst, an Army combat veteran, said she was sexually assaulted by an abusive boyfriend while she was a student at Iowa State University.
The Iowa Republican told Bloomberg she did not report the incident to police.