His name is most closely associated with nationalist Egyptian President Gamal Abdel Nasser in the 1960s.
Mr Heikal was the editor of Egypt's state-owned newspaper, Al-Ahram, during that time, articulating the Nasserist ideology of "Arab socialism".
He also served as information minister and briefly as foreign minister.
Following Nasser's death in 1970, Mr Heikal was sidelined by his successor Anwar al-Sadat. And in 1981 he was jailed along with hundreds of government critics.
He was released by Hosni Mubarak after Sadat's assassination by Islamist militants later that year, but was kept at arm's length by the president throughout his 29 years in office.
But Mr Heikal remained for decades one of the most authoritative commentators on Egypt and the Arab world - as well as a historian of the tumultuous events of the Nasser area.
Announcing Mr Heikal's death on Wednesday, Al-Ahram said he been ill for three weeks, and had suffered fluid on the lungs and kidney failure.
President Abdul Fattah al-Sisi paid tribute to Mr Heikal, calling him a "journalistic icon", while the cabinet said he had "massively participated in enriching intellectual life with his books, articles, political and historical studies", Egypt's ON TV Live reported.

The incident was reported at 13:45 BST on Saturday.
The Air Ambulance Northern Ireland airlifted the boy to the Royal Belfast Hospital for Sick Children where he is in a stable condition.
The callout was the first mission for the helicopter and its crew.
The air ambulance team is currently working through final preparations including training and familiarisation flights ahead of an official media launch of the service planned for early August.
However as a result of the serious nature of the incident, the aircraft was tasked to bring the Helicopter Emergency Medical Service (HEMS) doctor and paramedic to the scene.
Glenn O'Rorke, the operational lead for HEMS, said that the service will provide a doctor-paramedic team, for the whole of Northern Ireland, which will provide rapid interventions at the scene of where people have been injured before transferring patients to the appropriate hospital.
"It will make a huge difference to patients' lives and their outcome, it will improve their quality of life after injury because we will be there in a very short period of time," he said.
The campaign for the HEMS was begun by the late Dr John Hinds.
Northern Ireland was previously the only part in the UK without such a service.

Gales hitting 100mph (161 km/h) ripped through parts of Gwynedd in 2014, laying waste to the gardens at Plas Tan y Bwlch at Maentwrog.
A specialist consultant was recruited by the Snowdonia National Park Authority to restore the landscape to its former glory.
It involved planting 400 new plants - and has now erupted into colour.
"The gardens were originally created by the Oakeley family who owned the estate in the Victorian era," said Plas Tan y Bwlch's head of business, Andrew Oughton.
"They were particularly fond of magnolias, rhododendrons, camellias and Japanese maples, so we have planted new varieties of these, along with many other species."
The venue had to be closed initially following the storms in February 2014 and could not reopen until the summer.
But it has still needed another 18 months of constant work to clear fallen trees, replant shrubs and plants and reinstate paths.
New trails and a tearoom have also been installed as part of the restoration project.
"Only in the past few days everything has burst into flower, creating a spectacle of colour the like of which has not been seen for many years," added Mr Oughton.
One of the most famous and influential journalists in the Arab world, the Egyptian Mohamed Hassanein Heikal, has died in Cairo at the age of 92.
[NEXT_CONCEPT]
An 11-year-old boy has been seriously injured following an incident involving a tractor in the Castlewellan area of County Down.
[NEXT_CONCEPT]
A Victorian garden devastated by storms is back in full bloom in Snowdonia after two years of restoration work.