Fabius holds the distinction of being France's youngest ever prime minister, a post he took up at 37, and has remained a Socialist heavyweight, ending his career in the ornate hallways of the Quai d'Orsay as his country's top diplomat.
Amiable and sometimes witty in person, the cerebral 69-year-old also has a reputation for being aloof.
Nevertheless, his experience made him a popular foreign minister with the French people, who largely saw him as a fitting representative abroad.
Segolene Royal, the high-profile environment minister and ex-partner of President Francois Hollande, is among the rumoured successors, but former prime minister Jean-Marc Ayrault is also believed to be in the frame.
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As foreign minister since 2012, Fabius helped to negotiate the Iran nuclear deal, as well as dealing with the thorny dossiers of the Syria conflict, and the growing threat of jihadism in western Africa, where French troops are deployed.
However, it is Fabius's final big project that is likely to shape his legacy: sealing a historic deal to save mankind from global warning.
As host of the global climate talks at the end of 2015, he presided over 13 days of gruelling talks to get 195 nations to agree on transforming the energy system underlying the world economy.
While fending off rumours of ill health -- and a persistent suggestion that he suffered from Parkinson's -- Fabius threw himself into the complex world of climate science and politics for two years preceding the talks.
Fabius, who comes from a long line of art merchants, is independently wealthy, and his status as the richest of the Socialist ministers has been seen as off-putting to the rank and file.
Haughty, highly pedigreed and clad in classic suits -- Hermes, according to one local report -- he has often been labelled a member of the "gauche caviar", the French term for a champagne Socialist.