The alleged incident happened at the Police Scotland College at Tulliallan in Kincardine, Fife, on October 14.
Police Scotland said that an investigation was launched immediately and a police officer was suspended.
The college is a key training site for the force.
Assistant Chief Constable Alan Speirs said: “A report of a serious sexual assault was received on Friday October 14 2022 and an investigation by a team of specialist officers was launched immediately.
“An officer was also suspended at that time. He remains suspended while this investigation continues.”