The attack took place on Friday night in the Dumka district of the eastern state of Jharkhand, where the couple had stopped to camp the night in a tent.
The woman was able to reach a police patrol van at around 11:00 p.m. and was taken to hospital for treatment, police officer Pitamber Singh Kherwar told The Times of India newspaper.
Kherwar said police had detained three people in connection with the attack and were on the hunt for more suspects.
The Spanish woman is being treated at a local hospital in Dumka and an investigation is underway, reports said.
An average of nearly 90 rapes were reported in India every day in 2022, according to data by the National Crime Records Bureau.
However, large numbers go unreported due to prevailing stigmas around victims and a lack of faith in police investigations.