La-De-Dah.

We all remember the moment we first fell in love — and for many movie lovers, the moment sounded just like that.

Unconventional, iconoclastic and left-of-center, Diane Keaton arrived in our collective imagination by way of that three-syllable phrase — now synonymous with the freewheeling sensibility of an era — in ANNIE HALL (1977), one of the all-time great romantic comedies. Actor, artist, icon, Diane Keaton is certainly many things, but there is indisputably only one Diane Keaton.

With incomparable comic skill, pioneering fashion sense and unmistakable presence, she has illuminated our screens in comedies and dramas, catalyzed some of the best performances of all time — her costars’ and her own — and has also been the muse for master storytellers. To honor one of the greats of American film, the AFI Board of Trustees has selected Keaton as the recipient of the 45th AFI Life Achievement Award.

She was born Diane Hall on January 5, 1946 — at the birth of the baby boomer generation — just outside Hollywood in Highland Park, Los Angeles. She and her three siblings were raised by their mother, an artist, and father, a civil engineer who became a real estate broker. At age five, her family moved to Santa Ana, CA, where amid orange groves and tract homes she had an ordinary upbringing that she maintains always kept her grounded, even with her grand ambitions.

“I wanted to be a singer ever since I was five years old. I just never thought I wanted to be a star,” she said. Bitten by the performing bug as a kid, she organized herself and her siblings into a backyard theater troupe — when she wasn’t singing along with Doris Day and Judy Garland records or serenading the moon. “It was like plugging into a great big battery,” she said.

She made her public debut in high school talent shows and musicals including “Little Mary Sunshine,” and was one year anointed “Miss Personality.” She went on to study performing arts in local junior colleges, but the young talent quit at the behest of her drama coach, who believed that famed New York-based acting teacher Sanford Meisner could fully realize her potential. A leading light of the industry whose protégés included Gregory Peck and Grace Kelly, Meisner “changed everything,” Keaton said. “He introduced me to things I didn’t even know I had in me. He introduced me to rage. He introduced me to living in the moment.”

Her Meisner training propelled her to the stage. In 1968, she made her auspicious Broadway bow as an original cast member of the provocative rock musical “Hair.”

But everything changed when, later that year, Keaton auditioned for the Broadway production of “Play It Again, Sam,” written by a comedian named Woody Allen. He looked at countless actresses for the leading role of Linda but was instantly wowed by this quirky, offbeat ingénue.” Keaton was in a class by herself,” he said. She got the part — and later a Tony Award® nomination.

A screen version PLAY IT AGAIN, SAM (1972) also with Allen, followed — and moviegoers joined their love affair. Keaton proved to be a perfectly daffy screwball heroine, one half of a pairing as potent as Bogie and Bacall. And like that duo, Keaton and Allen became inextricably etched into the pop-culture consciousness.

“Her imprimatur was very meaningful to me, because I felt she was in touch with something deeper than I was,” Allen said. “She has had a definite influence on me. She’s a very gifted person.”

But Allen wasn’t the only director beguiled by Keaton’s charm. Enchanted by her punchy comic performance in her earlier film debut LOVERS AND OTHER STRANGERS (1970), Francis Ford Coppola cast her against type as Kay Adams, the long-suffering wife of a mafia heir, in back-to-back American masterpieces: THE GODFATHER (1972) and THE GODFATHER PART II (1974).

“She was so eccentric and weird in her delivery,” Coppola said. “Kay could be this really straight character, and I thought Diane could bring some eccentricity to it.”

As the wife of Al Pacino’s Michael Corleone, Keaton was an avatar for the audience, an outsider looking in — and nowhere does she embody this more chillingly than in the haunting final shot of THE GODFATHER, when Kay realizes her husband is a murderous gangster as a door slowly shuts in her face.

Critic David Thomson, praising Keaton’s “naïve bewilderment and loving distress,” wrote that her performance “contains all the mature, humane moments allowed into the dark fortress of THE GODFATHER.”

Throughout making THE GODFATHER films in the ’70s, Keaton kept collaborating closely with Allen, with delicious results in classics such as the slapstick sci-fi SLEEPER (1973) and hysterical Russian-literature satire LOVE AND DEATH (1975).

Then came ANNIE HALL.

Written by Allen as a valentine to Keaton and an ode to the happy-unhappy end of their real-life romance, this was the film that made her a global icon. Her loopy, delightfully ditzy demeanor and androgynous, Chaplinesque chic— a mélange of bolero hats, oversized tweeds, baggy pants and neckties — made her a sartorial symbol for designers everywhere.

“In ANNIE HALL, I was trying to give the audience the view of Diane that I had. If they can see her as I see her, they will love her,” Allen said.

Indeed, audiences and critics were enamored of her endearingly spacy, free-spirited, totally lovable and hilarious alter ego in this most modern New York love story. Keaton described the role as, “let’s face it, an affable version of myself. I never said ‘la-de-dah’ in my life until Woody wrote it. But I was a person who couldn’t complete a sentence, so he did get that right.”

And that affable version of herself won Keaton the Academy Award® for Best Actress — and the film Best Picture.

ANNIE HALL wasn’t Keaton’s only notable success in 1977. She also starred in the box office hit LOOKING FOR MR. GOODBAR, a gritty evocation of the shifting morals of the liberated post-Vietnam American climate, as an unlucky-in-love schoolteacher cruising singles bars. Acclaim for Keaton’s edgy performance was universal. The one-two punch of ANNIE HALL and MR. GOODBAR— along with Allen collaborations INTERIORS (1978) and MANHATTAN (1979) — proved this unorthodox movie maverick could slip easily between tragedy and farce.

That chameleonic quality caught the attention of another iconoclast — intrepid moviemaker Warren Beatty, who tapped Keaton for his ambitious epic REDS (1981). She starred as restlessly intelligent political writer Louise Bryant, opposite his radical journalist John Reed, circa the Russian Revolution. “If Diane Keaton had not made REDS, I don’t know what I would have done,” Beatty said. She earned a second Best Actress Academy Award® nomination for this plum role, which The New York Times called “the best work she has done to date.”

Keaton played another nonconformist in MRS. SOFFEL (1984), which was her first experience working under a female director. Gillian Armstrong inspired Keaton — long a passionate photographer — to go behind the movie camera for the first time. In 1987, she made her feature directing debut, HEAVEN, a passion-project documentary about the mysteries of the afterlife. This kicked off a busy directing career that would run alongside her acting for more than a decade, with stints on the TV series CHINA BEACH and TWIN PEAKS as well as the films UNSTRUNG HEROES (1995) and HANGING UP (2000). “I like to think that as a director I create an atmosphere of trust and, most important, play, in order to ease actors into the scary plunge of acting,” she said.

While making HEAVEN, Keaton returned to her comic roots for BABY BOOM (1987), a blockbuster that sparked timely debates about women in the corporate world. Written by Nancy Meyers — a key future collaborator — the film stars Keaton as an overachieving executive hilariously pratfalling while juggling her career and single motherhood. It was a showcase of her flair for embodying the many facets of an unconventional woman who fits no one particular mold.

“Diane is in the great tradition of the screen heroines I’ve always loved: Irene Dunne, Carole Lombard, Katharine Hepburn,” Meyers said. “She is so unpredictable that it makes everyone around her great.”

BABY BOOM launched a prolific period in which Keaton reteamed with her greatest collaborators — for Coppola’s THE GODFATHER PART III (1990), producer/writer Meyers’ FATHER OF THE BRIDE films (1991, 1995) and Allen’s MANHATTAN MURDER MYSTERY (1993).

Then, in 1996, Keaton once again proved the scope of her abilities across drama and comedy in a single year. She starred alongside Meryl Streep, Leonardo DiCaprio and Robert De Niro in the poignant MARVIN’S ROOM, for which she received yet another Academy Award® nomination — and she had a box-office smash starring with Goldie Hawn and Bette Midler in the funny fan favorite THE FIRST WIVES CLUB as a trio of women who find empowerment through divorce.

A self-described “late developer,” Keaton has never been married. But she did adopt children — her daughter Dexter in 1996 and her son Duke five years later. “To raise a child is the most humbling experience. It’s given my life a real purpose that it never had before,” she said.

Keaton’s tireless work ethic kept her on the screen and in the cultural zeitgeist. She reunited with director/writer Meyers for a return to funny form in SOMETHING’S GOTTA GIVE (2003), starring as a happily unmarried playwright thrown into chaos by the arrival of unexpected romance with both Keanu Reeves and Jack Nicholson. This wildly successful comedy revived the image of Keaton as the born comedian and reminded audiences of her trademark combination of vulnerability and strength — all culminating in her fourth Academy Award® nomination.

In the last decade, while still acting in winsome film comedies and on prestige TV — recently, HBO’s THE YOUNG POPE — Keaton has redefined herself (yet again) as a real-estate developer following in her father’s footsteps, an architectural advocate, a winemaker and an author of two bestselling memoirs that offer perhaps the most revealing snapshots yet of her life. While Keaton has long kept her private life private, she has enjoyed the creative freedom of few, and the celebrated American film career of even fewer — despite long dancing to her own tune through more than 80 credits across stage, page and screen.

“Diane is the most unique person that I’ve ever known,” Allen said. “That could be interpreted as weirdness, but she’s truly one of a kind.

One of a kind. There may be no better description of a movie star as enduring, inimitable and singular as Keaton. The American Film Institute tips its hat to one of cinema’s true originals with the AFI Life Achievement Award.