1 per director and i could only get it down to 11. Chrono order....

Pais (1946) - Rossellini 
Journal d'un cur de campagne (1951) - Bresson 
Tokyo monogatari (1953) - Ozu 
L'Avventura (1960) - Antononioni 
Vivre sa vie (1963) - Godard 
Teorema (1968) - Pasolini 
Il Conformista (1970) - Bertolucci 
Aguirre, der Zorn Gottes (1972) - Herzog 
Stalker (1979) - Tarkovsky 
Sans soleil (1983) - Marker 
La Belle noiseuse (1991) - Rivette 

Only 3 that aren't french or italian, strange. It's a dull list.

I don't class The Last Laugh as any language because it has no inter-titles, otherwise it'd be on this list.