Congo Belge Port de Matadi. Station du chemin de fer Matadi-Leopoldville. (French language)
Belgisch Congo Haven van Matadi. Stalie van den spoorweg Matadi-Leopoldville. (Dutch language)
Belgian Congo (now called: Democratic Republic of the Congo) Matadi Port. Matadi-Leopoldville Train Station.
This is postmarked in 1921 with a Belgian Congo stamp pre-printed on the postcard. It looks like there were two more stamps on the card, but someone took them off.