The old-fashioned musical--based on the 1967 Julie Andrews movie about a young flapper heading to New York in search of fame, fortune and a rich husband--also won Best Featured Actress (Harriet Harris), as well as in the choreography, costumes and orchestrations categories.
Winning Best Actress was extra sweet for Foster, considering the 27-year-old was originally an understudy for the part of Millie.
"To say that this is a dream come true is an understatement," a smiling Foster told the audience at New York's Radio City Music Hall, in a ceremony broadcast on PBS and CBS.
Overall, it was a fairly balanced affair, as the theater community doled out honors to its best and brightest in a year marred by the tragic terrorist attacks on the World Trade Center, which saw Broadway successfully rebound from a drastic drop in its bread-and-butter tourist industry.
Unlike last year's domination by Mel Brooks' smash hit The Producers, which grabbed a record-setting 12 Tonys, the awards were spread around this year.
Millie's toughest competition, Urinetown, might have lost out on Best Musical for poking fun at pay toilets and other musical genres. But the quirky little production, which originally premiered off-Broadway three years ago, still wound up with three prizes, including Best Book, Score and Direction.
Actor John Lithgow picked Best Male Actor in a Musical for his stint as a conniving gossip columnist on the beat in Sweet Smell of Success, the new musical based on the 1957 Hollywood movie. It was Lithgow's second career Tony.
Meanwhile, a revival of Stephen Sondheim's fractured fairy tale Into the Woods topped Oklahoma! for Best Musical Revival. Woods also nabbed the statuette for Best Lighting.
On the play side, several veterans of the theater returned to prominence, most notably three-time Pulitzer Prize-winning playwright Edward Albee, whose dark drama The Goat, or Who Is Sylvia?, about a man's love affair with a goat, collected Best Play. The award was Albee's second Tony in that category, his last win coming for Who's Afraid of Virginia Woolf in 1963.
"I don't get many rides to the Tonys," a delighted Albee said backstage. "Maybe it's nice to have them so infrequently."
Alan Bates and Frank Langella, who costarred in Fortune's Fool, Mike Poulton's adaptation of an 1848 Turgenev play, won for Best Actor and Featured Actor, respectively. It's been a long day's journey back to the spotlight as both men last won Tonys in the mid-'70s.
Meanwhile, 76-year-old Elaine Stritch burst into tears following her victory for Best Theatrical Event for her widely hailed one-woman show, Elaine Stritch at Liberty--but it wasn't from winning. Tony producers cut her acceptance speech short, opting to go to a commercial and leaving the Broadway legend somewhat bitter about the annual ritual.
"I'm very, very, very, very upset," an emotional Stritch, her voice cracking, told reporters afterwards. "It's pretty emotional for a woman my age to win her first Tony and to be cut down like that has spoiled it for me. And I mean that."
Not too surprisingly, Mary Zimmerman, whose play Metamorphoses updated the writings of ancient poet Ovid and was perhaps the most critically acclaimed production of the year, took home a Tony for Best Direction of a Play.
Scoring Best Revival was Private Lives, a comedy by the late great Noel Coward, which also earned best actress for Lindsay Duncan.
Such leading contenders as Mornings at Seven, which earned nine nods, and The Crucible, starring Best Actor and Actress nominees Liam Neeson and Laura Linney, which earned six, ended up with nothing. Also dissed was Mamma Mia!, the new musical based on the songs of Swedish '70s pop group ABBA, which had five nominations, and the drama Topdog/Underdog, which was this year's Pulitzer winner.
Here's a complete list of Tony winners, as selected by 702 members of the theatrical profession and journalists:
Play: The Goat, or Who Is Sylvia? Musical: Thoroughly Modern Millie Revival, Play: Private Lives Revival, Musical: Into the Woods Actor, Play: Alan Bates, Fortune's Fool Actress, Play: Lindsay Duncan, Private Lives Actor, Musical: John Lithgow, Sweet Smell of Success Actress, Musical: Sutton Foster, Thoroughly Modern Millie Featured Actor, Play: Frank Langella, Fortune's Fool Featured Actress, Play: Katie Finneran, Noises Off Featured Actor, Musical: Shuler Hensley, Oklahoma! Featured Actress, Musical: Harriet Harris, Thoroughly Modern Millie Director, Play: Mary Zimmerman, Metamorphoses Director, Musical: John Rando, Urinetown: The Musical Musical Book: Greg Kotis, Urinetown: The Musical Original Score: Mark Hollman (music), Mark Hollman & Greg Kotis (lyrics), Urinetown: The Musical Sceneic Design: Tim Hatley, Private Lives Costume Design: Martin Pakledinaz, Thoroughly Modern Millie Lighting Design: Brian MacDevitt, Into the Woods Choreography: Rob Ashford, Thoroughly Modern Millie Orchestrations: Doug Besterman and Ralph Burns, Thoroughly Modern Millie Special Awards for Lifetime Achievement: Julie Harris and Robert Whitehead Regional Theater Award: Williamstown Theater Festival