The owner of a 15-year-old mare believes she may have been stolen in Yorkshire.
Princess, described as being black and white with a black mane and tail, has gone missing from a field in the Kexbrough area of Barnsley.
She is very timid and nervous, police said.
She went missing from fields at Ballfield Lane, Kexbrough between 6pm on Wednesday 13 November and 9.30am on Thursday 14 November.
Her owner had left her in the field with two other horses, and fears she may have been stolen as there was no damage to any fencing or gates.
Police have asked anyone with information to contact 101 quoting crime reference number 14/172428/19 of 14 November.