Pippi Longstocking
Astrid Lindgren
From Sweden. Translated into a remarkable number of languages, so you can likely read it in yours.
Some of the best children's books were not written in English at all. For families with more than one language at home, these are also a good place to start swapping editions.
Astrid Lindgren
From Sweden. Translated into a remarkable number of languages, so you can likely read it in yours.
Kisszu
Characters named from five languages, available in English and Ukrainian.
Tove Jansson
From Finland, written in Swedish by Tove Jansson. No other book sounds like this.
Hervé Tullet
From France, and with so few words that it works in almost any language.