The Dutch daily De Telegraaf said the bone was found last Friday and is now being analyzed by forensic experts.
Tourists staying at the Phoenix Hotel discovered the bone on the beach and took it to the front desk, where a hotel employee alerted the police, a spokeswoman for Aruba prosecutors said.
The bone is damaged but would still be usable for DNA analysis or a comparison with dental records, the report says.
Holloway, then 18, went missing while on a trip to Aruba in May 2005 with her Mountain Brook, Ala., high-school classmates. Despite a major investigation, no concrete evidence of her death has ever been uncovered.
Much of the scrutiny in the case has focused on Joran van der Sloot, a Dutchman, now 23, who was living in Aruba at the time. He has been charged with trying to extort money from the Holloway family and is also accused of killing a Peruvian woman in a Lima hotel room this past May.