Serge Gainsbourg - L'étonnant Serge Gainsbourg (1961)

From allmusic (4/5):

"As early as 1961, Serge Gainsbourg was one of the most extraordinary artists of the French pop scene, and during the first part of the '60s the crooner produced a series of outrageously brilliant albums with producer/arranger Alain Goraguer. One of his most intoxicating amalgams of jazz and pop styles, L'Etonnant Serge Gainsbourg comes highly recommended to fans of '60s French pop. An utterly essential early document of Serge Gainsbourg while he was still a mildly respectable man -- but that's not say there aren't hints of his notorious decadence in this early work."

Get it here.

Also:
Serge Gainsbourg - N°2 (1959)
Serge Gainsbourg - L'Homme à Tête de Chou (1976)