In English:
* It's pronounced "alps" with a short "a" sound, like the word "alp" itself.
In French:
* It's pronounced "alp" with a silent "s" at the end.
In other languages:
* The pronunciation might vary slightly.
So, if you're referring to the Alps mountain range in English, you would say "alps." But if you're speaking French, you would say "alp."