Cllr Charmaine Morgan gave her entire 2019-20 South Kesteven District Council Ward Member Grant of £1,000 to the project, which together with £600 from Grantham Lions Club, meant the vital piece of equipment could be installed on the wall of the park office and public toilets building in Dysart Park.
Grantham Lions Club has previously provided a defibrillator for Wyndham Park.
Cllr Morgan, the chairman of SOS Grantham Hospital, said the installation was part of a project to install defibrillators in Grantham town centre and residential areas, and that she could not think of a better use of her grant than helping to provide equipment that might save someone's life.
Cllr Morgan said: "Defibrillators provide a safety net, particularly in view of the ongoing issues with the hospital, and the loss of its A&E. It is more vital than ever that we have life-saving equipment available to the public.
"This project has been a big team effort involving SKDC, the Lions, Dysart Park Action Group, SOS Grantham Hospital and myself."
The President of Grantham Lions Club, Godfrey Mackinder, joined Cllr Morgan and her SKDC colleague
Cllr Graham Jeal, a member of the Dysart Park Action Group, for the official unveiling of the defibrillator.
Cllr Jeal said: "Cardiac arrest can happen to anyone, young or old. The defibrillator is there just in case, and I'm sure visitors to Dysart Park will welcome the reassurance it provides. As vice-chairman of the Friends of Dysart Park, I am very grateful to everyone involved in making this happen."
Mr Mackinder said Dysart Park was a very popular public park used by a lot of people. He said: "It is one of those things you hope will never be needed, but it could be a vital piece of equipment, so the Lions Club was very happy to be able to help."
A defibrillator can be used to help restart the heart when someone has a cardiac arrest. For every minute that passes without defibrillation and CPR, chances of survival decrease by around 10%. In an emergency a 999 operator can direct the caller to their nearest defibrillator, and Dysart Park is now part of that network.