Alton Towers Spa has permanently closed after more than 20 years at the Staffordshire theme park.
The facility formed part of the original Alton Towers Hotel, and was open to the public all year.
Alton Towers, which is operated by Merlin Entertainments, said that the decision was taken after “careful consideration”.
It added that it viewed the decision as “essential for the future growth and development” of the resort.
The park’s website previously showed 31 December as being the last opening day for the spa.
Alton Towers said it was contacting guests with bookings for 2024, suggesting the move to close was only made recently.
Opened in its current form in 2003, the spa offered various forms of treatments including facials and massages.
Its swimming pool was originally the pool built as part of the original Alton Towers Hotel in 1996.
The space occupied by the spa is now widely expected to be repurposed to expand hotel facilities.