Ethereal, elegant, beautiful, Catherine Deneuve has provoked awe from critics and cineasts for 30 years. Today, at 51, she's as ethereal, elegant, and beautiful as ever, but equally striking is the self-assurance of an actress who's cannily made the most of the auteur theory. ''I've always been more choosy for directors than parts,'' she says, which helps explain her run with the likes of Truffaut (The Last Metro), Polanski (Repulsion), and Buñuel (Tristana), all of whom eagerly mined the talent behind her beauty.

Deneuve established her career as an innocent in 1963's Umbrellas of Cherbourg, only to shock French critics as the housewife-turned-prostitute in Buñuel's 1967 Belle de Jour, now in re-release. Today, Deneuve still enjoys the film's dry wit, playfully calling its ambiguous shifts between fantasy and reality ''interactive.'' Despite the international acclaim Belle de Jour won her, Deneuve was wasted in the U.S. in trifles like 1969's April Fools and 1975's Hustle and is better known here for her chic Chanel perfume ads. Still, she'd give Hollywood another try, with an edgy American director like Quentin Tarantino or Martin Scorsese, of whom she says, ''His love for film reminds me of Truffaut.''

Still in demand in France, Deneuve followed her Oscar-nominated role in 1992's Indochine with last year's Ma Saison Préférée, which costarred her daughter, Chiara, 23, whose father is Marcello Mastroianni. (Her son, Christian, 32, by director Roger Vadim, is also an actor.) She's now shooting her 68th film, Child of the Night. Denueve says she has yet to play her real age, but recent parts mark a transition to so-called mature roles. ''After 40 it's difficult, especially in a profession where appearance is so important,'' she confesses. ''I don't think too much about it. Maybe if I were working less, it would be different.''

So how does Belle de Jour's cool blond view today's screen sex? ''People naked on screen seem very fragile,'' Deneuve says. ''I find it more erotic when they're dressed.'' The actress, who played a vampire in '83's The Hunger, also has refined taste in horror. ''I love the Dracula of Coppola. But I don't like movies where people are sawed up,'' she shudders. ''I like horror films that just give you a little, you know, fizzle on the skin.'' Mais, oui.