It happened at around 3am yesterday, August 27, on the beach near the junction of West Street and King’s Road.
A 22-year-old man from Brighton has been arrested on suspicion of attempted rape and remains in police custody at this time.
A Sussex Police spokesman said: “The victim is receiving support from specially trained officers.
“Police are appealing for witnesses or anyone with further information to contact them.
“Information can be reported to Sussex Police online or by calling 101 and quoting serial 233 of 27/08.”