Serge Gainsbourg - Histoire de Melody Nelson (1971)

From allmusic (4.5/5):

"You don't need to speak a word of French to understand Histoire de Melody Nelson — one needs only to look at the front cover (with its nearly pornographic portrait of a half-naked nymphet clutching a rag doll) or hear the lechery virtually dripping from Serge Gainsbourg's sleazily seductive voice to realize that this is the record your mother always warned you about, a masterpiece of perversion and corruption. A concept record exploring the story of — and Gainsbourg's lust for — the titular teen heroine, Histoire de Melody Nelson is arguably his most coherent and perfectly realized studio album, with the lush arrangements which characterize the majority of his work often mixed here with funky rhythm lines which underscore the musky allure of the music. Perhaps best described as a dirty old bastard's attempt to make his own R&B love-man's record along the lines of a Let's Get It On (itself still two years away from release), it's by turns fascinating and repellent, hilarious and grim, but never dull — which, in Gainsbourg's world, would be the ultimate (and quite possibly the only) sin."

Get it here.

Also:
Serge Gainsbourg - N°2 (1959)
Serge Gainsbourg - L'étonnant Serge Gainsbourg (1961)
Jane Birkin et Serge Gainsbourg (1969)
Serge Gainsbourg - L'Homme à Tête de Chou (1976)