The woman, aged in her 40s, has reported that she was attacked while staying at a five-star hotel at the Red Sea resort of Sharm-el-Sheikh.
She has claimed that she was sexually assaulted by a guard who had been escorting her to her room.
A spokesman for Hampshire police said: "Officers from Hampshire Constabulary's specialist interview team are currently assisting with an investigation into a serious sexual assault of an English woman which is reported to have occurred in the Sharm-el-Sheikh region of Egypt on March 6."
A Foreign and Commonwealth Office (FCO) spokesman confirmed that it was aware of the incident.
He said: "We are aware of an incident involving a British national and we are providing consular assistance."
The FCO website warns travellers of a rise in such attacks in the country.
It states: "Reports of cases of sexual assault against British nationals have increased during and since the unrest of early 2011.
"In 2012, the FCO handled 23 cases of sexual assault and six cases of rape. Some assaults were against minors. Many occurred in what were considered to be safe places such as hotels."