Sussex Police, assisted by the National Police Air Service (NPAS) and South East Coast Ambulance Service (SECAmb), were called to a property in Crowborough shortly after 8pm.
They were responding to reports of a woman being attacked by a dog in the garden of a property in Hoadleys Lane.
A police spokesperson said: "The woman was brought to safety and taken to hospital with potentially life-changing injuries.
"The dog was contained in the garden, with the support of National Police Air Service helicopter and has since been seized by officers."