His birthday bash will take place a week later in Zimbabwe's best-known tourist resort of Victoria Falls.
But the opposition Movement for Democratic Change (MDC) says that holding a lavish party at a time when the country’s economy is in crisis is wrong.
MDC spokesperson Obert Gutu called Mugabe's party an “obscene jamboree”.
A 91-year-old man would be better off in an old-age home, he suggested in comments that are almost certain to anger Mugabe's ruling Zanu-PF.
The birthday party is to be held at a golf course in one of the plushest hotels in Victoria Falls and organisers are going all out to make it one of the best the president's supporters will remember.
Zanu-PF hasn't confirmed press reports that it will cost more than 870,000 euros, much of that raised through donations.
The party is holding fund-raising dinners around the country.
Members of Zimbabwe’s struggling business community have said they've been asked to part with up to 175 euros for a plate of food.
The MDC says the funds raised should be donated to collapsed schools and clinics in Matabeleland North province, where the Victoria Falls are located.