"It is with great sadness that we report that Nora Ephron has died," her publisher Alfred A. Knopf, said in a statement. "She brought an awful lot of people a tremendous amount of joy. She will be sorely missed."
The New York Times cited her son, Jacob Bernstein, as saying Ephron died. Bernstein is a freelance reporter for the Times.
"From her earliest days at New York City's newspapers to her biggest Hollywood successes, Nora always loved a good New York story, and she could tell them like no one else," Bloomberg said in a statement.
Ephron, who often parlayed her own love life into movies like "Heartburn" and gave her acerbic take on aging in the 2010 essay collection, "I Remember Nothing: And Other Reflections," had kept her illness largely private except for close friends and family.
The elegant Ephron, known for habitually dressing in black, urged aging friends and readers to make the most of their lives.
"You should eat delicious things while you can still eat them, go to wonderful places while you still can ... and not have evenings where you say to yourself, 'What am I doing here? Why am I here? I am bored witless!'" she told Reuters in a 2010 interview while promoting the book.
She began her career as a journalist but transitioned into movies, leaving behind a legacy of more than a dozen films, often featuring strong female characters, that she either wrote, produced or directed. She was nominated for three Academy Awards for "Harry Met Sally," "Sleepless in Seattle" and the drama "Silkwood" with Meryl Streep playing an anti-nuclear activist.
Ephron also wrote for the stage, authoring the 2002 play "Imaginary Friends" about the rivalry of authors Mary McCarthy and Lillian Hellman, and "Love, Loss and What I Wore," with her sister Delia, in 2009.
New York, Washington, Hollywood
Born May 19, 1941 in New York City and raised in Beverly Hills by screenwriter parents, Ephron worked briefly as a White House intern before going into journalism. She quickly became known as a humorist with essays on subjects ranging from food and fashion to feminism.
She helped rewrite a version of the script for the movie "All The President's Men," about Bernstein and Bob Woodward's uncovering of the political scandal that led to the resignation of Richard Nixon in 1974. Although that screenplay was not used, it led to a TV movie screenwriting job for Ephron.
Her big movie break came after a messy divorce from Bernstein, which was the genesis for her 1983 novel "Heartburn" that she later adapted into the bittersweet hit film of the same name starring Jack Nicholson and Meryl Streep.
"Sleepless in Seattle" and "You've Got Mail," that saw Ephron gradually add producer and director to her resume and become one of Hollywood's most successful makers of romantic comedies.
Although her movies raked in tens of millions of dollars at box offices worldwide, Ephron never won the industry's highest honor, an Academy Award.
After box office flops "Hanging Up" and "Lucky Numbers" in 2000, Ephron focused on essays, writing for the stage, and blogging for the online news site The Huffington Post.
Her humorous 2006 collection "I Feel Bad About My Neck: And Other Thoughts on Being a Woman" became a bestseller on the New York Times list.
Ephron was married three times and is survived by her husband of more than 20 years, writer Nicholas Pileggi, and two children with Bernstein.
(Additional reporting By Piya Sinha-Roy.; Editing by Christopher Wilson and Philip Barbara)