Police are investigating the incident and are appealing for witnesses and information.
The incident was at the Accident and Emergency entrance, just off Lancaster Park road at around 5:20am
A North Yorkshire Police spokesman said:
Police were called to reports of a theft from an ambulance outside Harrogate General Hospital at around 6.20am this morning.
Medical equipment and clothing has been reported missing from the vehicle.
Our officers are currently investigating the incident and anyone with information is asked to contact North Yorkshire Police on 101, quoting reference number 12160072602.