Resnais, whose play-within-a-film "Life of Riley" (Aimer, boire et chanter) won a prize for innovation at the Berlin Film Festival last month, died in Paris late "surrounded by his family," said his producer Jean-Louis Livi.
With a shock of wiry white hair and trademark dark shades, Resnais was a much-loved figure of the French film world and a regular presence at top festivals from Cannes to Berlin.
France's foreign minister, Laurent Fabius, paid tribute to "a very great talent, universally known".
Resnais's first slot at the Cannes Film Festival was for the New Wave classic "Hiroshima Mon Amour", screened out of competition in 1959.
Still making movies as he reached 90 — with recurring themes of love, memory and mortality — he told Cannes two years ago he made films "for myself, like DIY".
"It's like a laboratory experiment in which you mix things without knowing what the result will be."
At the time of his death, he was working on the script for a new film, according to Livi, who produced his most recent works.
Born on June 3rd, 1922 in the western city of Vannes, Resnais made a short film on the storybook villain "Fantomas" at the tender age of 13.
Riding the crest of the French New Wave of the 1960s, he stood slightly apart from his contemporaries Jean-Luc Godard, Jacques Rivette and Francois Truffaut.
While they filmed young Parisians in the streets with hand-held cameras, Resnais played with narrative "flash-ins" that mingled past and present.
His early features like "Hiroshima mon Amour" and "L'Annee Derniere a Marienbad" (1961) drew on the work of modernist French authors Marguerite Duras and Alain Robbe-Grillet.
From the 1970s onwards, Resnais' films became lighter and more accessible, and his quasi-musical "On Connait la Chanson" (The Same Old Song, 1998) was a huge commercial and critical success.
But he remained one of the most experimental French filmmakers, with often-present themes on fractured time and parallel worlds.
The Cannes festival awarded him a lifetime achievement award in 2009.
Resnais married twice, and is survived by his second wife, Sabine Azema.